/[pcre]/code/trunk/doc/pcre.txt

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-revision 429 by ph10,
Tue Sep  1 16:10:16 2009 UTC
+revision 535 by ph10,
Thu Jun  3 19:18:24 2010 UTC
 Line 2
  This file contains a concatenation of the PCRE man pages, converted to plain
  text format for ease of searching with a text editor, or for use on systems
  that do not have a man page processor. The small individual files that give
  synopses of each function in the library have not been included. Neither has
  the pcredemo program. There are separate text files for the pcregrep and
  pcretest commands.
  -----------------------------------------------------------------------------
 Line 19 
 INTRODUCTION
         The  PCRE  library is a set of functions that implement regular expres-
         sion pattern matching using the same syntax and semantics as Perl, with
-        just  a  few  differences. Certain features that appeared in Python and
+        just  a few differences. Some features that appeared in Python and PCRE
-        PCRE before they appeared in Perl are also available using  the  Python
+        before they appeared in Perl are also available using the  Python  syn-
-        syntax.  There is also some support for certain .NET and Oniguruma syn-
+        tax,  there  is  some  support for one or two .NET and Oniguruma syntax
-        tax items, and there is an option for  requesting  some  minor  changes
+        items, and there is an option for requesting some  minor  changes  that
-        that give better JavaScript compatibility.
+        give better JavaScript compatibility.
-        The  current implementation of PCRE (release 8.xx) corresponds approxi-
+        The  current implementation of PCRE corresponds approximately with Perl
-        mately with Perl 5.10, including support for UTF-8 encoded strings  and
+.10/5.11, including support for UTF-8 encoded strings and Unicode gen-
-        Unicode general category properties. However, UTF-8 and Unicode support
+        eral  category properties. However, UTF-8 and Unicode support has to be
-        has to be explicitly enabled; it is not the default. The Unicode tables
+        explicitly enabled; it is not the default. The  Unicode  tables  corre-
-        correspond to Unicode release 5.1.
+        spond to Unicode release 5.2.0.
         In  addition to the Perl-compatible matching function, PCRE contains an
-        alternative matching function that matches the same  compiled  patterns
+        alternative function that matches the same compiled patterns in a  dif-
-        in  a different way. In certain circumstances, the alternative function
+        ferent way. In certain circumstances, the alternative function has some
-        has some advantages. For a discussion of the two  matching  algorithms,
+        advantages.  For a discussion of the two matching algorithms,  see  the
-        see the pcrematching page.
+        pcrematching page.
         PCRE  is  written  in C and released as a C library. A number of people
         have written wrappers and interfaces of various kinds.  In  particular,
 Line 55 
 INTRODUCTION
         library is built. The pcre_config() function makes it  possible  for  a
         client  to  discover  which  features are available. The features them-
         selves are described in the pcrebuild page. Documentation about  build-
-        ing  PCRE for various operating systems can be found in the README file
+        ing  PCRE  for various operating systems can be found in the README and
-        in the source distribution.
+        NON-UNIX-USE files in the source distribution.
         The library contains a number of undocumented  internal  functions  and
         data  tables  that  are  used by more than one of the exported external
 Line 89 
 USER DOCUMENTATION
           pcrepartial       details of the partial matching facility
           pcrepattern       syntax and semantics of supported
                               regular expressions
-          pcresyntax        quick syntax reference
           pcreperform       discussion of performance issues
           pcreposix         the POSIX-compatible C API
           pcreprecompile    details of saving and re-using precompiled patterns
           pcresample        discussion of the pcredemo program
           pcrestack         discussion of stack usage
+          pcresyntax        quick syntax reference
           pcretest          description of the pcretest testing command
         In  addition,  in the "man" and HTML formats, there is a short page for
 Line 142 
 UTF-8 AND UNICODE PROPERTY SUPPORT
         with  the  PCRE_UTF8  option  flag,  or the pattern must start with the
         sequence (*UTF8). When either of these is the case,  both  the  pattern
         and  any  subject  strings  that  are matched against it are treated as
-        UTF-8 strings instead of just strings of bytes.
+        UTF-8 strings instead of strings of 1-byte characters.
         If you compile PCRE with UTF-8 support, but do not use it at run  time,
         the  library will be a bit bigger, but the additional run time overhead
 Line 222 
 UTF-8 AND UNICODE PROPERTY SUPPORT
         not available in the alternative matching function, pcre_dfa_exec().
 .  The  character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly
-        test characters of any code value, but the characters that PCRE  recog-
+        test characters of any code value, but, by default, the characters that
-        nizes  as  digits,  spaces,  or  word characters remain the same set as
+        PCRE  recognizes  as digits, spaces, or word characters remain the same
-        before, all with values less than 256. This remains true even when PCRE
+        set as before, all with values less than 256. This  remains  true  even
-        includes  Unicode  property support, because to do otherwise would slow
+        when  PCRE  is built to include Unicode property support, because to do
-        down PCRE in many common cases. If you really want to test for a  wider
+        otherwise would slow down PCRE in many common  cases.  Note  that  this
-        sense  of,  say,  "digit",  you must use Unicode property tests such as
+        also applies to \b, because it is defined in terms of \w and \W. If you
-        \p{Nd}. Note that this also applies to \b, because  it  is  defined  in
+        really want to test for a wider sense of, say,  "digit",  you  can  use
-        terms of \w and \W.
+        explicit  Unicode property tests such as \p{Nd}.  Alternatively, if you
+        set the PCRE_UCP option, the way that the  character  escapes  work  is
+        changed  so that Unicode properties are used to determine which charac-
+        ters match. There are more details in the section on generic  character
+        types in the pcrepattern documentation.
 .  Similarly,  characters that match the POSIX named character classes
-        are all low-valued characters.
+        are all low-valued characters, unless the PCRE_UCP option is set.
 . However, the Perl 5.10 horizontal and vertical  whitespace  matching
         escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-
-        acters.
+        acters, whether or not PCRE_UCP is set.
 . Case-insensitive matching applies only to  characters  whose  values
         are  less than 128, unless PCRE is built with Unicode property support.
-Line 263 
 AUTHOR
+Line 267 
 AUTHOR
  REVISION
-        Last updated: 01 September 2009
+        Last updated: 12 May 2010
-        Copyright (c) 1997-2009 University of Cambridge.
+        Copyright (c) 1997-2010 University of Cambridge.
  ------------------------------------------------------------------------------
  PCREBUILD(3)                                                      PCREBUILD(3)
-Line 282 
 PCRE BUILD-TIME OPTIONS
+Line 286 
 PCRE BUILD-TIME OPTIONS
         script,  where the optional features are selected or deselected by pro-
         viding options to configure before running the make  command.  However,
         the  same  options  can be selected in both Unix-like and non-Unix-like
-        environments using the GUI facility of  CMakeSetup  if  you  are  using
+        environments using the GUI facility of cmake-gui if you are using CMake
-        CMake instead of configure to build PCRE.
+        instead of configure to build PCRE.
+        There  is  a  lot more information about building PCRE in non-Unix-like
+        environments in the file called NON_UNIX_USE, which is part of the PCRE
+        distribution.  You  should consult this file as well as the README file
+        if you are building in a non-Unix-like environment.
         The complete list of options for configure (which includes the standard
-        ones such as the  selection  of  the  installation  directory)  can  be
+        ones  such  as  the  selection  of  the  installation directory) can be
         obtained by running
           ./configure --help
-        The  following  sections  include  descriptions  of options whose names
+        The following sections include  descriptions  of  options  whose  names
         begin with --enable or --disable. These settings specify changes to the
-        defaults  for  the configure command. Because of the way that configure
+        defaults for the configure command. Because of the way  that  configure
-        works, --enable and --disable always come in pairs, so  the  complemen-
+        works,  --enable  and --disable always come in pairs, so the complemen-
-        tary  option always exists as well, but as it specifies the default, it
+        tary option always exists as well, but as it specifies the default,  it
         is not described.
-Line 316 
 UTF-8 SUPPORT
+Line 325 
 UTF-8 SUPPORT
           --enable-utf8
-        to the configure command. Of itself, this  does  not  make  PCRE  treat
+        to  the  configure  command.  Of  itself, this does not make PCRE treat
-        strings  as UTF-8. As well as compiling PCRE with this option, you also
+        strings as UTF-8. As well as compiling PCRE with this option, you  also
-        have have to set the PCRE_UTF8 option when you call the  pcre_compile()
+        have  have to set the PCRE_UTF8 option when you call the pcre_compile()
-        function.
+        or pcre_compile2() functions.
-        If  you set --enable-utf8 when compiling in an EBCDIC environment, PCRE
+        If you set --enable-utf8 when compiling in an EBCDIC environment,  PCRE
         expects its input to be either ASCII or UTF-8 (depending on the runtime
-        option).  It  is not possible to support both EBCDIC and UTF-8 codes in
+        option). It is not possible to support both EBCDIC and UTF-8  codes  in
-        the same  version  of  the  library.  Consequently,  --enable-utf8  and
+        the  same  version  of  the  library.  Consequently,  --enable-utf8 and
         --enable-ebcdic are mutually exclusive.
  UNICODE CHARACTER PROPERTY SUPPORT
-        UTF-8  support allows PCRE to process character values greater than 255
+        UTF-8 support allows PCRE to process character values greater than  255
-        in the strings that it handles. On its own, however, it does  not  pro-
+        in  the  strings that it handles. On its own, however, it does not pro-
         vide any facilities for accessing the properties of such characters. If
-        you want to be able to use the pattern escapes \P, \p,  and  \X,  which
+        you  want  to  be able to use the pattern escapes \P, \p, and \X, which
         refer to Unicode character properties, you must add
           --enable-unicode-properties
-        to  the configure command. This implies UTF-8 support, even if you have
+        to the configure command. This implies UTF-8 support, even if you  have
         not explicitly requested it.
-        Including Unicode property support adds around 30K  of  tables  to  the
+        Including  Unicode  property  support  adds around 30K of tables to the
-        PCRE  library.  Only  the general category properties such as Lu and Nd
+        PCRE library. Only the general category properties such as  Lu  and  Nd
         are supported. Details are given in the pcrepattern documentation.
  CODE VALUE OF NEWLINE
-        By default, PCRE interprets the linefeed (LF) character  as  indicating
+        By  default,  PCRE interprets the linefeed (LF) character as indicating
-        the  end  of  a line. This is the normal newline character on Unix-like
+        the end of a line. This is the normal newline  character  on  Unix-like
-        systems. You can compile PCRE to use carriage return (CR)  instead,  by
+        systems.  You  can compile PCRE to use carriage return (CR) instead, by
         adding
           --enable-newline-is-cr
-        to  the  configure  command.  There  is  also  a --enable-newline-is-lf
+        to the  configure  command.  There  is  also  a  --enable-newline-is-lf
         option, which explicitly specifies linefeed as the newline character.
         Alternatively, you can specify that line endings are to be indicated by
-Line 367 
 CODE VALUE OF NEWLINE
+Line 376 
 CODE VALUE OF NEWLINE
           --enable-newline-is-anycrlf
-        which  causes  PCRE  to recognize any of the three sequences CR, LF, or
+        which causes PCRE to recognize any of the three sequences  CR,  LF,  or
         CRLF as indicating a line ending. Finally, a fifth option, specified by
           --enable-newline-is-any
         causes PCRE to recognize any Unicode newline sequence.
-        Whatever line ending convention is selected when PCRE is built  can  be
+        Whatever  line  ending convention is selected when PCRE is built can be
-        overridden  when  the library functions are called. At build time it is
+        overridden when the library functions are called. At build time  it  is
         conventional to use the standard for your operating system.
  WHAT \R MATCHES
-        By default, the sequence \R in a pattern matches  any  Unicode  newline
+        By  default,  the  sequence \R in a pattern matches any Unicode newline
-        sequence,  whatever  has  been selected as the line ending sequence. If
+        sequence, whatever has been selected as the line  ending  sequence.  If
         you specify
           --enable-bsr-anycrlf
-        the default is changed so that \R matches only CR, LF, or  CRLF.  What-
+        the  default  is changed so that \R matches only CR, LF, or CRLF. What-
-        ever  is selected when PCRE is built can be overridden when the library
+        ever is selected when PCRE is built can be overridden when the  library
         functions are called.
  BUILDING SHARED AND STATIC LIBRARIES
-        The PCRE building process uses libtool to build both shared and  static
+        The  PCRE building process uses libtool to build both shared and static
-        Unix  libraries by default. You can suppress one of these by adding one
+        Unix libraries by default. You can suppress one of these by adding  one
         of
           --disable-shared
-Line 407 
 BUILDING SHARED AND STATIC LIBRARIES
+Line 416 
 BUILDING SHARED AND STATIC LIBRARIES
  POSIX MALLOC USAGE
         When PCRE is called through the POSIX interface (see the pcreposix doc-
-        umentation),  additional  working  storage  is required for holding the
+        umentation), additional working storage is  required  for  holding  the
-        pointers to capturing substrings, because PCRE requires three  integers
+        pointers  to capturing substrings, because PCRE requires three integers
-        per  substring,  whereas  the POSIX interface provides only two. If the
+        per substring, whereas the POSIX interface provides only  two.  If  the
         number of expected substrings is small, the wrapper function uses space
         on the stack, because this is faster than using malloc() for each call.
         The default threshold above which the stack is no longer used is 10; it
-Line 422 
 POSIX MALLOC USAGE
+Line 431 
 POSIX MALLOC USAGE
  HANDLING VERY LARGE PATTERNS
-        Within  a  compiled  pattern,  offset values are used to point from one
+        Within a compiled pattern, offset values are used  to  point  from  one
-        part to another (for example, from an opening parenthesis to an  alter-
+        part  to another (for example, from an opening parenthesis to an alter-
-        nation  metacharacter).  By default, two-byte values are used for these
+        nation metacharacter). By default, two-byte values are used  for  these
-        offsets, leading to a maximum size for a  compiled  pattern  of  around
+        offsets,  leading  to  a  maximum size for a compiled pattern of around
-K.  This  is sufficient to handle all but the most gigantic patterns.
+K. This is sufficient to handle all but the most  gigantic  patterns.
-        Nevertheless, some people do want to process enormous patterns,  so  it
+        Nevertheless,  some  people do want to process truyl enormous patterns,
-        is  possible  to compile PCRE to use three-byte or four-byte offsets by
+        so it is possible to compile PCRE to use three-byte or  four-byte  off-
-        adding a setting such as
+        sets by adding a setting such as
           --with-link-size=3
-        to the configure command. The value given must be 2,  3,  or  4.  Using
+        to  the  configure  command.  The value given must be 2, 3, or 4. Using
-        longer  offsets slows down the operation of PCRE because it has to load
+        longer offsets slows down the operation of PCRE because it has to  load
         additional bytes when handling them.
  AVOIDING EXCESSIVE STACK USAGE
         When matching with the pcre_exec() function, PCRE implements backtrack-
-        ing  by  making recursive calls to an internal function called match().
+        ing by making recursive calls to an internal function  called  match().
-        In environments where the size of the stack is limited,  this  can  se-
+        In  environments  where  the size of the stack is limited, this can se-
-        verely  limit  PCRE's operation. (The Unix environment does not usually
+        verely limit PCRE's operation. (The Unix environment does  not  usually
         suffer from this problem, but it may sometimes be necessary to increase
-        the  maximum  stack size.  There is a discussion in the pcrestack docu-
+        the maximum stack size.  There is a discussion in the  pcrestack  docu-
-        mentation.) An alternative approach to recursion that uses memory  from
+        mentation.)  An alternative approach to recursion that uses memory from
-        the  heap  to remember data, instead of using recursive function calls,
+        the heap to remember data, instead of using recursive  function  calls,
-        has been implemented to work round the problem of limited  stack  size.
+        has  been  implemented to work round the problem of limited stack size.
         If you want to build a version of PCRE that works this way, add
           --disable-stack-for-recursion
-        to  the  configure  command. With this configuration, PCRE will use the
+        to the configure command. With this configuration, PCRE  will  use  the
-        pcre_stack_malloc and pcre_stack_free variables to call memory  manage-
+        pcre_stack_malloc  and pcre_stack_free variables to call memory manage-
-        ment  functions. By default these point to malloc() and free(), but you
+        ment functions. By default these point to malloc() and free(), but  you
-        can replace the pointers so that your own functions are used.
+        can replace the pointers so that your own functions are used instead.
-        Separate functions are  provided  rather  than  using  pcre_malloc  and
+        Separate  functions  are  provided  rather  than  using pcre_malloc and
-        pcre_free  because  the  usage  is  very  predictable:  the block sizes
+        pcre_free because the  usage  is  very  predictable:  the  block  sizes
-        requested are always the same, and  the  blocks  are  always  freed  in
+        requested  are  always  the  same,  and  the blocks are always freed in
-        reverse  order.  A calling program might be able to implement optimized
+        reverse order. A calling program might be able to  implement  optimized
-        functions that perform better  than  malloc()  and  free().  PCRE  runs
+        functions  that  perform  better  than  malloc()  and free(). PCRE runs
         noticeably more slowly when built in this way. This option affects only
-        the  pcre_exec()  function;  it   is   not   relevant   for   the   the
+        the pcre_exec() function; it is not relevant for pcre_dfa_exec().
-        pcre_dfa_exec() function.
  LIMITING PCRE RESOURCE USAGE
-Line 554 
 PCRETEST OPTION FOR LIBREADLINE SUPPORT
+Line 562 
 PCRETEST OPTION FOR LIBREADLINE SUPPORT
         to  the  configure  command,  pcretest  is  linked with the libreadline
         library, and when its input is from a terminal, it reads it  using  the
         readline() function. This provides line-editing and history facilities.
-        Note that libreadline is GPL-licenced, so if you distribute a binary of
+        Note that libreadline is GPL-licensed, so if you distribute a binary of
         pcretest linked in this way, there may be licensing issues.
         Setting  this  option  causes  the -lreadline option to be added to the
-Line 590 
 AUTHOR
+Line 598 
 AUTHOR
  REVISION
-        Last updated: 17 March 2009
+        Last updated: 29 September 2009
         Copyright (c) 1997-2009 University of Cambridge.
  ------------------------------------------------------------------------------
  PCREMATCHING(3)                                                PCREMATCHING(3)
-Line 678 
 THE ALTERNATIVE MATCHING ALGORITHM
+Line 686 
 THE ALTERNATIVE MATCHING ALGORITHM
         though  it is not implemented as a traditional finite state machine (it
         keeps multiple states active simultaneously).
+        Although the general principle of this matching algorithm  is  that  it
+        scans  the subject string only once, without backtracking, there is one
+        exception: when a lookaround assertion is encountered,  the  characters
+        following  or  preceding  the  current  point  have to be independently
+        inspected.
         The scan continues until either the end of the subject is  reached,  or
         there  are  no more unterminated paths. At this point, terminated paths
         represent the different matching possibilities (if there are none,  the
         match  has  failed).   Thus,  if there is more than one possible match,
         this algorithm finds all of them, and in particular, it finds the long-
-        est.  In PCRE, there is an option to stop the algorithm after the first
+        est.  There  is  an  option to stop the algorithm after the first match
-        match (which is necessarily the shortest) has been found.
+        (which is necessarily the shortest) is found.
         Note that all the matches that are found start at the same point in the
         subject. If the pattern
-Line 757 
 ADVANTAGES OF THE ALTERNATIVE ALGORITHM
+Line 771 
 ADVANTAGES OF THE ALTERNATIVE ALGORITHM
 .  Because  the  alternative  algorithm  scans the subject string just
         once, and never needs to backtrack, it is possible to  pass  very  long
         subject  strings  to  the matching function in several pieces, checking
-        for partial matching each time.
+        for partial matching each time.  The  pcrepartial  documentation  gives
+        details of partial matching.
  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
         The alternative algorithm suffers from a number of disadvantages:
-. It is substantially slower than  the  standard  algorithm.  This  is
+.  It  is  substantially  slower  than the standard algorithm. This is
-        partly  because  it has to search for all possible matches, but is also
+        partly because it has to search for all possible matches, but  is  also
         because it is less susceptible to optimization.
 . Capturing parentheses and back references are not supported.
-Line 783 
 AUTHOR
+Line 798 
 AUTHOR
  REVISION
-        Last updated: 25 August 2009
+        Last updated: 29 September 2009
         Copyright (c) 1997-2009 University of Cambridge.
  ------------------------------------------------------------------------------
  PCREAPI(3)                                                          PCREAPI(3)
-Line 891 
 PCRE API OVERVIEW
+Line 906 
 PCRE API OVERVIEW
         bers for the library.  Applications can use these  to  include  support
         for different releases of PCRE.
+        In a Windows environment, if you want to statically link an application
+        program against a non-dll pcre.a  file,  you  must  define  PCRE_STATIC
+        before  including  pcre.h or pcrecpp.h, because otherwise the pcre_mal-
+        loc()   and   pcre_free()   exported   functions   will   be   declared
+        __declspec(dllimport), with unwanted results.
         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
         pcre_exec() are used for compiling and matching regular expressions  in
         a  Perl-compatible  manner. A sample program that demonstrates the sim-
-Line 902 
 PCRE API OVERVIEW
+Line 923 
 PCRE API OVERVIEW
         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
         ble, is also provided. This uses a different algorithm for  the  match-
         ing.  The  alternative algorithm finds all possible matches (at a given
-        point in the subject), and scans the subject just once.  However,  this
+        point in the subject), and scans the subject just  once  (unless  there
-        algorithm does not return captured substrings. A description of the two
+        are  lookbehind  assertions).  However,  this algorithm does not return
-        matching algorithms and their advantages and disadvantages is given  in
+        captured substrings. A description of the two matching  algorithms  and
-        the pcrematching documentation.
+        their  advantages  and disadvantages is given in the pcrematching docu-
+        mentation.
-        In  addition  to  the  main compiling and matching functions, there are
+        In addition to the main compiling and  matching  functions,  there  are
         convenience functions for extracting captured substrings from a subject
         string that is matched by pcre_exec(). They are:
-Line 922 
 PCRE API OVERVIEW
+Line 944 
 PCRE API OVERVIEW
         pcre_free_substring() and pcre_free_substring_list() are also provided,
         to free the memory used for extracted strings.
-        The function pcre_maketables() is used to  build  a  set  of  character
+        The  function  pcre_maketables()  is  used  to build a set of character
-        tables   in   the   current   locale  for  passing  to  pcre_compile(),
+        tables  in  the  current  locale   for   passing   to   pcre_compile(),
-        pcre_exec(), or pcre_dfa_exec(). This is an optional facility  that  is
+        pcre_exec(),  or  pcre_dfa_exec(). This is an optional facility that is
-        provided  for  specialist  use.  Most  commonly,  no special tables are
+        provided for specialist use.  Most  commonly,  no  special  tables  are
-        passed, in which case internal tables that are generated when  PCRE  is
+        passed,  in  which case internal tables that are generated when PCRE is
         built are used.
-        The  function  pcre_fullinfo()  is used to find out information about a
+        The function pcre_fullinfo() is used to find out  information  about  a
-        compiled pattern; pcre_info() is an obsolete version that returns  only
+        compiled  pattern; pcre_info() is an obsolete version that returns only
-        some  of  the available information, but is retained for backwards com-
+        some of the available information, but is retained for  backwards  com-
-        patibility.  The function pcre_version() returns a pointer to a  string
+        patibility.   The function pcre_version() returns a pointer to a string
         containing the version of PCRE and its date of release.
-        The  function  pcre_refcount()  maintains  a  reference count in a data
+        The function pcre_refcount() maintains a  reference  count  in  a  data
-        block containing a compiled pattern. This is provided for  the  benefit
+        block  containing  a compiled pattern. This is provided for the benefit
         of object-oriented applications.
-        The  global  variables  pcre_malloc and pcre_free initially contain the
+        The global variables pcre_malloc and pcre_free  initially  contain  the
-        entry points of the standard malloc()  and  free()  functions,  respec-
+        entry  points  of  the  standard malloc() and free() functions, respec-
         tively. PCRE calls the memory management functions via these variables,
-        so a calling program can replace them if it  wishes  to  intercept  the
+        so  a  calling  program  can replace them if it wishes to intercept the
         calls. This should be done before calling any PCRE functions.
-        The  global  variables  pcre_stack_malloc  and pcre_stack_free are also
+        The global variables pcre_stack_malloc  and  pcre_stack_free  are  also
-        indirections to memory management functions.  These  special  functions
+        indirections  to  memory  management functions. These special functions
-        are  used  only  when  PCRE is compiled to use the heap for remembering
+        are used only when PCRE is compiled to use  the  heap  for  remembering
         data, instead of recursive function calls, when running the pcre_exec()
-        function.  See  the  pcrebuild  documentation  for details of how to do
+        function. See the pcrebuild documentation for  details  of  how  to  do
-        this. It is a non-standard way of building PCRE, for  use  in  environ-
+        this.  It  is  a non-standard way of building PCRE, for use in environ-
-        ments  that  have  limited stacks. Because of the greater use of memory
+        ments that have limited stacks. Because of the greater  use  of  memory
-        management, it runs more slowly. Separate  functions  are  provided  so
+        management,  it  runs  more  slowly. Separate functions are provided so
-        that  special-purpose  external  code  can  be used for this case. When
+        that special-purpose external code can be  used  for  this  case.  When
-        used, these functions are always called in a  stack-like  manner  (last
+        used,  these  functions  are always called in a stack-like manner (last
-        obtained,  first freed), and always for memory blocks of the same size.
+        obtained, first freed), and always for memory blocks of the same  size.
-        There is a discussion about PCRE's stack usage in the  pcrestack  docu-
+        There  is  a discussion about PCRE's stack usage in the pcrestack docu-
         mentation.
         The global variable pcre_callout initially contains NULL. It can be set
-        by the caller to a "callout" function, which PCRE  will  then  call  at
+        by  the  caller  to  a "callout" function, which PCRE will then call at
-        specified  points during a matching operation. Details are given in the
+        specified points during a matching operation. Details are given in  the
         pcrecallout documentation.
  NEWLINES
-        PCRE supports five different conventions for indicating line breaks  in
+        PCRE  supports five different conventions for indicating line breaks in
-        strings:  a  single  CR (carriage return) character, a single LF (line-
+        strings: a single CR (carriage return) character, a  single  LF  (line-
         feed) character, the two-character sequence CRLF, any of the three pre-
-        ceding,  or any Unicode newline sequence. The Unicode newline sequences
+        ceding, or any Unicode newline sequence. The Unicode newline  sequences
-        are the three just mentioned, plus the single characters  VT  (vertical
+        are  the  three just mentioned, plus the single characters VT (vertical
-        tab,  U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
+        tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS  (line
         separator, U+2028), and PS (paragraph separator, U+2029).
-        Each of the first three conventions is used by at least  one  operating
+        Each  of  the first three conventions is used by at least one operating
-        system  as its standard newline sequence. When PCRE is built, a default
+        system as its standard newline sequence. When PCRE is built, a  default
-        can be specified.  The default default is LF, which is the  Unix  stan-
+        can  be  specified.  The default default is LF, which is the Unix stan-
-        dard.  When  PCRE  is run, the default can be overridden, either when a
+        dard. When PCRE is run, the default can be overridden,  either  when  a
         pattern is compiled, or when it is matched.
         At compile time, the newline convention can be specified by the options
-        argument  of  pcre_compile(), or it can be specified by special text at
+        argument of pcre_compile(), or it can be specified by special  text  at
         the start of the pattern itself; this overrides any other settings. See
         the pcrepattern page for details of the special character sequences.
         In the PCRE documentation the word "newline" is used to mean "the char-
-        acter or pair of characters that indicate a line break". The choice  of
+        acter  or pair of characters that indicate a line break". The choice of
-        newline  convention  affects  the  handling of the dot, circumflex, and
+        newline convention affects the handling of  the  dot,  circumflex,  and
         dollar metacharacters, the handling of #-comments in /x mode, and, when
-        CRLF  is a recognized line ending sequence, the match position advance-
+        CRLF is a recognized line ending sequence, the match position  advance-
         ment for a non-anchored pattern. There is more detail about this in the
         section on pcre_exec() options below.
-        The  choice of newline convention does not affect the interpretation of
+        The choice of newline convention does not affect the interpretation  of
-        the \n or \r escape sequences, nor does  it  affect  what  \R  matches,
+        the  \n  or  \r  escape  sequences, nor does it affect what \R matches,
         which is controlled in a similar way, but by separate options.
  MULTITHREADING
-        The  PCRE  functions  can be used in multi-threading applications, with
+        The PCRE functions can be used in  multi-threading  applications,  with
         the  proviso  that  the  memory  management  functions  pointed  to  by
         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
         callout function pointed to by pcre_callout, are shared by all threads.
-        The compiled form of a regular expression is not altered during  match-
+        The  compiled form of a regular expression is not altered during match-
         ing, so the same compiled pattern can safely be used by several threads
         at once.
-Line 1014 
 MULTITHREADING
+Line 1036 
 MULTITHREADING
  SAVING PRECOMPILED PATTERNS FOR LATER USE
         The compiled form of a regular expression can be saved and re-used at a
-        later  time,  possibly by a different program, and even on a host other
+        later time, possibly by a different program, and even on a  host  other
-        than the one on which  it  was  compiled.  Details  are  given  in  the
+        than  the  one  on  which  it  was  compiled.  Details are given in the
-        pcreprecompile  documentation.  However, compiling a regular expression
+        pcreprecompile documentation. However, compiling a  regular  expression
-        with one version of PCRE for use with a different version is not  guar-
+        with  one version of PCRE for use with a different version is not guar-
         anteed to work and may cause crashes.
-Line 1025 
 CHECKING BUILD-TIME OPTIONS
+Line 1047 
 CHECKING BUILD-TIME OPTIONS
         int pcre_config(int what, void *where);
-        The  function pcre_config() makes it possible for a PCRE client to dis-
+        The function pcre_config() makes it possible for a PCRE client to  dis-
         cover which optional features have been compiled into the PCRE library.
-        The  pcrebuild documentation has more details about these optional fea-
+        The pcrebuild documentation has more details about these optional  fea-
         tures.
-        The first argument for pcre_config() is an  integer,  specifying  which
+        The  first  argument  for pcre_config() is an integer, specifying which
         information is required; the second argument is a pointer to a variable
-        into which the information is  placed.  The  following  information  is
+        into  which  the  information  is  placed. The following information is
         available:
           PCRE_CONFIG_UTF8
-        The  output is an integer that is set to one if UTF-8 support is avail-
+        The output is an integer that is set to one if UTF-8 support is  avail-
         able; otherwise it is set to zero.
           PCRE_CONFIG_UNICODE_PROPERTIES
-        The output is an integer that is set to  one  if  support  for  Unicode
+        The  output  is  an  integer  that is set to one if support for Unicode
         character properties is available; otherwise it is set to zero.
           PCRE_CONFIG_NEWLINE
-        The  output  is  an integer whose value specifies the default character
+        The output is an integer whose value specifies  the  default  character
-        sequence that is recognized as meaning "newline". The four values  that
+        sequence  that is recognized as meaning "newline". The four values that
         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
-        and -1 for ANY.  Though they are derived from ASCII,  the  same  values
+        and  -1  for  ANY.  Though they are derived from ASCII, the same values
         are returned in EBCDIC environments. The default should normally corre-
         spond to the standard sequence for your operating system.
           PCRE_CONFIG_BSR
         The output is an integer whose value indicates what character sequences
-        the  \R  escape sequence matches by default. A value of 0 means that \R
+        the \R escape sequence matches by default. A value of 0 means  that  \R
-        matches any Unicode line ending sequence; a value of 1  means  that  \R
+        matches  any  Unicode  line ending sequence; a value of 1 means that \R
         matches only CR, LF, or CRLF. The default can be overridden when a pat-
         tern is compiled or matched.
           PCRE_CONFIG_LINK_SIZE
-        The output is an integer that contains the number  of  bytes  used  for
+        The  output  is  an  integer that contains the number of bytes used for
         internal linkage in compiled regular expressions. The value is 2, 3, or
-. Larger values allow larger regular expressions to  be  compiled,  at
+.  Larger  values  allow larger regular expressions to be compiled, at
-        the  expense  of  slower matching. The default value of 2 is sufficient
+        the expense of slower matching. The default value of  2  is  sufficient
-        for all but the most massive patterns, since  it  allows  the  compiled
+        for  all  but  the  most massive patterns, since it allows the compiled
         pattern to be up to 64K in size.
           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
-        The  output  is  an integer that contains the threshold above which the
+        The output is an integer that contains the threshold  above  which  the
-        POSIX interface uses malloc() for output vectors. Further  details  are
+        POSIX  interface  uses malloc() for output vectors. Further details are
         given in the pcreposix documentation.
           PCRE_CONFIG_MATCH_LIMIT
-        The  output is a long integer that gives the default limit for the num-
+        The output is a long integer that gives the default limit for the  num-
-        ber of internal matching function calls  in  a  pcre_exec()  execution.
+        ber  of  internal  matching  function calls in a pcre_exec() execution.
         Further details are given with pcre_exec() below.
           PCRE_CONFIG_MATCH_LIMIT_RECURSION
         The output is a long integer that gives the default limit for the depth
-        of  recursion  when  calling  the  internal  matching  function  in   a
+        of   recursion  when  calling  the  internal  matching  function  in  a
-        pcre_exec()  execution.  Further  details  are  given  with pcre_exec()
+        pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
         below.
           PCRE_CONFIG_STACKRECURSE
-        The output is an integer that is set to one if internal recursion  when
+        The  output is an integer that is set to one if internal recursion when
         running pcre_exec() is implemented by recursive function calls that use
-        the stack to remember their state. This is the usual way that  PCRE  is
+        the  stack  to remember their state. This is the usual way that PCRE is
         compiled. The output is zero if PCRE was compiled to use blocks of data
-        on the  heap  instead  of  recursive  function  calls.  In  this  case,
+        on  the  heap  instead  of  recursive  function  calls.  In  this case,
-        pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory
+        pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory
         blocks on the heap, thus avoiding the use of the stack.
-Line 1114 
 COMPILING A PATTERN
+Line 1136 
 COMPILING A PATTERN
         Either of the functions pcre_compile() or pcre_compile2() can be called
         to compile a pattern into an internal form. The only difference between
-        the two interfaces is that pcre_compile2() has an additional  argument,
+        the  two interfaces is that pcre_compile2() has an additional argument,
-        errorcodeptr, via which a numerical error code can be returned.
+        errorcodeptr, via which a numerical error  code  can  be  returned.  To
+        avoid  too  much repetition, we refer just to pcre_compile() below, but
+        the information applies equally to pcre_compile2().
         The pattern is a C string terminated by a binary zero, and is passed in
-        the pattern argument. A pointer to a single block  of  memory  that  is
+        the  pattern  argument.  A  pointer to a single block of memory that is
-        obtained  via  pcre_malloc is returned. This contains the compiled code
+        obtained via pcre_malloc is returned. This contains the  compiled  code
         and related data. The pcre type is defined for the returned block; this
         is a typedef for a structure whose contents are not externally defined.
         It is up to the caller to free the memory (via pcre_free) when it is no
         longer required.
-        Although  the compiled code of a PCRE regex is relocatable, that is, it
+        Although the compiled code of a PCRE regex is relocatable, that is,  it
         does not depend on memory location, the complete pcre data block is not
-        fully  relocatable, because it may contain a copy of the tableptr argu-
+        fully relocatable, because it may contain a copy of the tableptr  argu-
         ment, which is an address (see below).
         The options argument contains various bit settings that affect the com-
-        pilation.  It  should be zero if no options are required. The available
+        pilation. It should be zero if no options are required.  The  available
-        options are described below. Some of them (in  particular,  those  that
+        options  are  described  below. Some of them (in particular, those that
-        are  compatible  with  Perl,  but also some others) can also be set and
+        are compatible with Perl, but some others as well) can also be set  and
-        unset from within the pattern (see  the  detailed  description  in  the
+        unset  from  within  the  pattern  (see the detailed description in the
-        pcrepattern  documentation). For those options that can be different in
+        pcrepattern documentation). For those options that can be different  in
-        different parts of the pattern, the contents of  the  options  argument
+        different  parts  of  the pattern, the contents of the options argument
-        specifies their initial settings at the start of compilation and execu-
+        specifies their settings at the start of compilation and execution. The
-        tion. The PCRE_ANCHORED and PCRE_NEWLINE_xxx options can be set at  the
+        PCRE_ANCHORED, PCRE_BSR_xxx, and PCRE_NEWLINE_xxx options can be set at
-        time of matching as well as at compile time.
+        the time of matching as well as at compile time.
         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
-        if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and
+        if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
         sets the variable pointed to by errptr to point to a textual error mes-
         sage. This is a static string that is part of the library. You must not
-        try to free it. The offset from the start of the pattern to the charac-
+        try to free it. The byte offset from the start of the  pattern  to  the
-        ter where the error was discovered is placed in the variable pointed to
+        character  that  was  being  processed when the error was discovered is
-        by  erroffset,  which must not be NULL. If it is, an immediate error is
+        placed in the variable pointed to by erroffset, which must not be NULL.
-        given.
+        If  it  is,  an  immediate error is given. Some errors are not detected
+        until checks are carried out when the whole pattern has  been  scanned;
-        If pcre_compile2() is used instead of pcre_compile(),  and  the  error-
+        in this case the offset is set to the end of the pattern.
-        codeptr  argument is not NULL, a non-zero error code number is returned
-        via this argument in the event of an error. This is in addition to  the
+        If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
+        codeptr argument is not NULL, a non-zero error code number is  returned
+        via  this argument in the event of an error. This is in addition to the
         textual error message. Error codes and messages are listed below.
-        If  the  final  argument, tableptr, is NULL, PCRE uses a default set of
+        If the final argument, tableptr, is NULL, PCRE uses a  default  set  of
-        character tables that are  built  when  PCRE  is  compiled,  using  the
+        character  tables  that  are  built  when  PCRE  is compiled, using the
-        default  C  locale.  Otherwise, tableptr must be an address that is the
+        default C locale. Otherwise, tableptr must be an address  that  is  the
-        result of a call to pcre_maketables(). This value is  stored  with  the
+        result  of  a  call to pcre_maketables(). This value is stored with the
-        compiled  pattern,  and used again by pcre_exec(), unless another table
+        compiled pattern, and used again by pcre_exec(), unless  another  table
         pointer is passed to it. For more discussion, see the section on locale
         support below.
-        This  code  fragment  shows a typical straightforward call to pcre_com-
+        This code fragment shows a typical straightforward  call  to  pcre_com-
         pile():
           pcre *re;
-Line 1176 
 COMPILING A PATTERN
+Line 1202 
 COMPILING A PATTERN
             &erroffset,       /* for error offset */
             NULL);            /* use default character tables */
-        The following names for option bits are defined in  the  pcre.h  header
+        The  following  names  for option bits are defined in the pcre.h header
         file:
           PCRE_ANCHORED
         If this bit is set, the pattern is forced to be "anchored", that is, it
-        is constrained to match only at the first matching point in the  string
+        is  constrained to match only at the first matching point in the string
-        that  is being searched (the "subject string"). This effect can also be
+        that is being searched (the "subject string"). This effect can also  be
-        achieved by appropriate constructs in the pattern itself, which is  the
+        achieved  by appropriate constructs in the pattern itself, which is the
         only way to do it in Perl.
           PCRE_AUTO_CALLOUT
         If this bit is set, pcre_compile() automatically inserts callout items,
-        all with number 255, before each pattern item. For  discussion  of  the
+        all  with  number  255, before each pattern item. For discussion of the
         callout facility, see the pcrecallout documentation.
           PCRE_BSR_ANYCRLF
           PCRE_BSR_UNICODE
         These options (which are mutually exclusive) control what the \R escape
-        sequence matches. The choice is either to match only CR, LF,  or  CRLF,
+        sequence  matches.  The choice is either to match only CR, LF, or CRLF,
         or to match any Unicode newline sequence. The default is specified when
         PCRE is built. It can be overridden from within the pattern, or by set-
         ting an option when a compiled pattern is matched.
           PCRE_CASELESS
-        If  this  bit is set, letters in the pattern match both upper and lower
+        If this bit is set, letters in the pattern match both upper  and  lower
-        case letters. It is equivalent to Perl's  /i  option,  and  it  can  be
+        case  letters.  It  is  equivalent  to  Perl's /i option, and it can be
-        changed  within a pattern by a (?i) option setting. In UTF-8 mode, PCRE
+        changed within a pattern by a (?i) option setting. In UTF-8 mode,  PCRE
-        always understands the concept of case for characters whose values  are
+        always  understands the concept of case for characters whose values are
-        less  than 128, so caseless matching is always possible. For characters
+        less than 128, so caseless matching is always possible. For  characters
-        with higher values, the concept of case is supported if  PCRE  is  com-
+        with  higher  values,  the concept of case is supported if PCRE is com-
-        piled  with Unicode property support, but not otherwise. If you want to
+        piled with Unicode property support, but not otherwise. If you want  to
-        use caseless matching for characters 128 and  above,  you  must  ensure
+        use  caseless  matching  for  characters 128 and above, you must ensure
-        that  PCRE  is  compiled  with Unicode property support as well as with
+        that PCRE is compiled with Unicode property support  as  well  as  with
         UTF-8 support.
           PCRE_DOLLAR_ENDONLY
-        If this bit is set, a dollar metacharacter in the pattern matches  only
+        If  this bit is set, a dollar metacharacter in the pattern matches only
-        at  the  end  of the subject string. Without this option, a dollar also
+        at the end of the subject string. Without this option,  a  dollar  also
-        matches immediately before a newline at the end of the string (but  not
+        matches  immediately before a newline at the end of the string (but not
-        before  any  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored
+        before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
-        if PCRE_MULTILINE is set.  There is no equivalent  to  this  option  in
+        if  PCRE_MULTILINE  is  set.   There is no equivalent to this option in
         Perl, and no way to set it within a pattern.
           PCRE_DOTALL
         If this bit is set, a dot metacharater in the pattern matches all char-
-        acters, including those that indicate newline. Without it, a  dot  does
+        acters,  including  those that indicate newline. Without it, a dot does
-        not  match  when  the  current position is at a newline. This option is
+        not match when the current position is at a  newline.  This  option  is
-        equivalent to Perl's /s option, and it can be changed within a  pattern
+        equivalent  to Perl's /s option, and it can be changed within a pattern
-        by  a (?s) option setting. A negative class such as [^a] always matches
+        by a (?s) option setting. A negative class such as [^a] always  matches
         newline characters, independent of the setting of this option.
           PCRE_DUPNAMES
-        If this bit is set, names used to identify capturing  subpatterns  need
+        If  this  bit is set, names used to identify capturing subpatterns need
         not be unique. This can be helpful for certain types of pattern when it
-        is known that only one instance of the named  subpattern  can  ever  be
+        is  known  that  only  one instance of the named subpattern can ever be
-        matched.  There  are  more details of named subpatterns below; see also
+        matched. There are more details of named subpatterns  below;  see  also
         the pcrepattern documentation.
           PCRE_EXTENDED
-        If this bit is set, whitespace  data  characters  in  the  pattern  are
+        If  this  bit  is  set,  whitespace  data characters in the pattern are
         totally ignored except when escaped or inside a character class. White-
         space does not include the VT character (code 11). In addition, charac-
         ters between an unescaped # outside a character class and the next new-
-        line, inclusive, are also ignored. This  is  equivalent  to  Perl's  /x
+        line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
-        option,  and  it  can be changed within a pattern by a (?x) option set-
+        option, and it can be changed within a pattern by a  (?x)  option  set-
         ting.
-        This option makes it possible to include  comments  inside  complicated
+        This  option  makes  it possible to include comments inside complicated
-        patterns.   Note,  however,  that this applies only to data characters.
+        patterns.  Note, however, that this applies only  to  data  characters.
-        Whitespace  characters  may  never  appear  within  special   character
+        Whitespace   characters  may  never  appear  within  special  character
-        sequences  in  a  pattern,  for  example  within the sequence (?( which
+        sequences in a pattern, for  example  within  the  sequence  (?(  which
         introduces a conditional subpattern.
           PCRE_EXTRA
-        This option was invented in order to turn on  additional  functionality
+        This  option  was invented in order to turn on additional functionality
-        of  PCRE  that  is  incompatible with Perl, but it is currently of very
+        of PCRE that is incompatible with Perl, but it  is  currently  of  very
-        little use. When set, any backslash in a pattern that is followed by  a
+        little  use. When set, any backslash in a pattern that is followed by a
-        letter  that  has  no  special  meaning causes an error, thus reserving
+        letter that has no special meaning  causes  an  error,  thus  reserving
-        these combinations for future expansion. By  default,  as  in  Perl,  a
+        these  combinations  for  future  expansion.  By default, as in Perl, a
-        backslash  followed by a letter with no special meaning is treated as a
+        backslash followed by a letter with no special meaning is treated as  a
-        literal. (Perl can, however, be persuaded to give a warning for  this.)
+        literal. (Perl can, however, be persuaded to give an error for this, by
-        There  are  at  present no other features controlled by this option. It
+        running it with the -w option.) There are at present no other  features
-        can also be set by a (?X) option setting within a pattern.
+        controlled  by this option. It can also be set by a (?X) option setting
+        within a pattern.
           PCRE_FIRSTLINE
-Line 1355 
 COMPILING A PATTERN
+Line 1382 
 COMPILING A PATTERN
         be  used  for  capturing  (and  they acquire numbers in the usual way).
         There is no equivalent of this option in Perl.
+          PCRE_UCP
+        This option changes the way PCRE processes \b, \d, \s, \w, and some  of
+        the POSIX character classes. By default, only ASCII characters are rec-
+        ognized, but if PCRE_UCP is set, Unicode properties are used instead to
+        classify  characters.  More details are given in the section on generic
+        character types in the pcrepattern page. If you set PCRE_UCP,  matching
+        one  of the items it affects takes much longer. The option is available
+        only if PCRE has been compiled with Unicode property support.
           PCRE_UNGREEDY
         This option inverts the "greediness" of the quantifiers  so  that  they
-Line 1453 
 COMPILATION ERROR CODES
+Line 1490 
 COMPILATION ERROR CODES
  \g is not followed by a braced, angle-bracketed, or quoted
                 name/number or by a plain number
  a numbered reference must not be zero
- (*VERB) with an argument is not supported
+ an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
  (*VERB) not recognized
  number is too big
  subpattern name expected
  digit expected after (?+
  ] is an invalid data character in JavaScript compatibility mode
+  different  names  for  subpatterns  of  the  same number are not
+        allowed
+ (*MARK) must have an argument
+ this version of PCRE is not compiled with PCRE_UCP support
-        The  numbers  32  and 10000 in errors 48 and 49 are defaults; different
+        The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different
         values may be used if the limits were changed when PCRE was built.
-Line 1469 
 STUDYING A PATTERN
+Line 1510 
 STUDYING A PATTERN
         pcre_extra *pcre_study(const pcre *code, int options
              const char **errptr);
-        If a compiled pattern is going to be used several times,  it  is  worth
+        If  a  compiled  pattern is going to be used several times, it is worth
         spending more time analyzing it in order to speed up the time taken for
-        matching. The function pcre_study() takes a pointer to a compiled  pat-
+        matching.  The function pcre_study() takes a pointer to a compiled pat-
         tern as its first argument. If studying the pattern produces additional
-        information that will help speed up matching,  pcre_study()  returns  a
+        information  that  will  help speed up matching, pcre_study() returns a
-        pointer  to a pcre_extra block, in which the study_data field points to
+        pointer to a pcre_extra block, in which the study_data field points  to
         the results of the study.
         The  returned  value  from  pcre_study()  can  be  passed  directly  to
-        pcre_exec().  However,  a  pcre_extra  block also contains other fields
+        pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block  also  con-
-        that can be set by the caller before the block  is  passed;  these  are
+        tains  other  fields  that can be set by the caller before the block is
-        described below in the section on matching a pattern.
+        passed; these are described below in the section on matching a pattern.
-        If  studying  the  pattern  does not produce any additional information
+        If studying the  pattern  does  not  produce  any  useful  information,
         pcre_study() returns NULL. In that circumstance, if the calling program
-        wants  to  pass  any of the other fields to pcre_exec(), it must set up
+        wants  to  pass  any  of   the   other   fields   to   pcre_exec()   or
-        its own pcre_extra block.
+        pcre_dfa_exec(), it must set up its own pcre_extra block.
-        The second argument of pcre_study() contains option bits.  At  present,
+        The  second  argument of pcre_study() contains option bits. At present,
         no options are defined, and this argument should always be zero.
-        The  third argument for pcre_study() is a pointer for an error message.
+        The third argument for pcre_study() is a pointer for an error  message.
-        If studying succeeds (even if no data is  returned),  the  variable  it
+        If  studying  succeeds  (even  if no data is returned), the variable it
-        points  to  is  set  to NULL. Otherwise it is set to point to a textual
+        points to is set to NULL. Otherwise it is set to  point  to  a  textual
         error message. This is a static string that is part of the library. You
-        must  not  try  to  free it. You should test the error pointer for NULL
+        must not try to free it. You should test the  error  pointer  for  NULL
         after calling pcre_study(), to be sure that it has run successfully.
         This is a typical call to pcre_study():
-Line 1505 
 STUDYING A PATTERN
+Line 1546 
 STUDYING A PATTERN
 ,              /* no options exist */
             &error);        /* set to NULL or points to a message */
-        At present, studying a pattern is useful only for non-anchored patterns
+        Studying a pattern does two things: first, a lower bound for the length
-        that  do not have a single fixed starting character. A bitmap of possi-
+        of subject string that is needed to match the pattern is computed. This
-        ble starting bytes is created.
+        does not mean that there are any strings of that length that match, but
+        it does guarantee that no shorter strings match. The value is  used  by
+        pcre_exec()  and  pcre_dfa_exec()  to  avoid  wasting time by trying to
+        match strings that are shorter than the lower bound. You can  find  out
+        the value in a calling program via the pcre_fullinfo() function.
+        Studying a pattern is also useful for non-anchored patterns that do not
+        have a single fixed starting character. A bitmap of  possible  starting
+        bytes  is  created. This speeds up finding a position in the subject at
+        which to start matching.
  LOCALE SUPPORT
-Line 1515 
 LOCALE SUPPORT
+Line 1565 
 LOCALE SUPPORT
         PCRE handles caseless matching, and determines whether  characters  are
         letters,  digits, or whatever, by reference to a set of tables, indexed
         by character value. When running in UTF-8 mode, this  applies  only  to
-        characters  with  codes  less than 128. Higher-valued codes never match
+        characters  with  codes  less than 128. By default, higher-valued codes
-        escapes such as \w or \d, but can be tested with \p if  PCRE  is  built
+        never match escapes such as \w or \d, but they can be tested with \p if
-        with  Unicode  character property support. The use of locales with Uni-
+        PCRE  is  built with Unicode character property support. Alternatively,
-        code is discouraged. If you are handling characters with codes  greater
+        the PCRE_UCP option can be set at compile  time;  this  causes  \w  and
-        than  128, you should either use UTF-8 and Unicode, or use locales, but
+        friends to use Unicode property support instead of built-in tables. The
-        not try to mix the two.
+        use of locales with Unicode is discouraged. If you are handling charac-
+        ters  with codes greater than 128, you should either use UTF-8 and Uni-
+        code, or use locales, but not try to mix the two.
         PCRE contains an internal set of tables that are used  when  the  final
         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many
-Line 1673 
 INFORMATION ABOUT A PATTERN
+Line 1725 
 INFORMATION ABOUT A PATTERN
         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
         /^a\dz\d/ the returned value is -1.
+          PCRE_INFO_MINLENGTH
+        If the pattern was studied and a minimum length  for  matching  subject
+        strings  was  computed,  its  value is returned. Otherwise the returned
+        value is -1. The value is a number of characters, not bytes  (this  may
+        be  relevant in UTF-8 mode). The fourth argument should point to an int
+        variable. A non-negative value is a lower bound to the  length  of  any
+        matching  string.  There  may not be any strings of that length that do
+        actually match, but every string that does match is at least that long.
           PCRE_INFO_NAMECOUNT
           PCRE_INFO_NAMEENTRYSIZE
           PCRE_INFO_NAMETABLE
-Line 1694 
 INFORMATION ABOUT A PATTERN
+Line 1756 
 INFORMATION ABOUT A PATTERN
         a pointer to the first entry of the table  (a  pointer  to  char).  The
         first two bytes of each entry are the number of the capturing parenthe-
         sis, most significant byte first. The rest of the entry is  the  corre-
-        sponding  name,  zero  terminated. The names are in alphabetical order.
+        sponding name, zero terminated.
-        When PCRE_DUPNAMES is set, duplicate names are in order of their paren-
-        theses  numbers.  For  example,  consider the following pattern (assume
+        The  names are in alphabetical order. Duplicate names may appear if (?|
-        PCRE_EXTENDED is  set,  so  white  space  -  including  newlines  -  is
+        is used to create multiple groups with the same number, as described in
-        ignored):
+        the  section  on  duplicate subpattern numbers in the pcrepattern page.
+        Duplicate names for subpatterns with different  numbers  are  permitted
+        only  if  PCRE_DUPNAMES  is  set. In all cases of duplicate names, they
+        appear in the table in the order in which they were found in  the  pat-
+        tern.  In  the  absence  of (?| this is the order of increasing number;
+        when (?| is used this is not necessarily the case because later subpat-
+        terns may have lower numbers.
+        As  a  simple  example of the name/number table, consider the following
+        pattern (assume PCRE_EXTENDED is set, so white space -  including  new-
+        lines - is ignored):
           (?<date> (?<year>(\d\d)?\d\d) -
           (?<month>\d\d) - (?<day>\d\d) )
-Line 1719 
 INFORMATION ABOUT A PATTERN
+Line 1791 
 INFORMATION ABOUT A PATTERN
           PCRE_INFO_OKPARTIAL
-        Return 1 if the pattern can be used for partial matching, otherwise  0.
+        Return 1  if  the  pattern  can  be  used  for  partial  matching  with
-        The fourth argument should point to an int variable. From release 8.00,
+        pcre_exec(),  otherwise  0.  The fourth argument should point to an int
-        this always returns 1, because the restrictions that previously applied
+        variable. From  release  8.00,  this  always  returns  1,  because  the
-        to  partial  matching  have  been lifted. The pcrepartial documentation
+        restrictions  that  previously  applied  to  partial matching have been
-        gives details of partial matching.
+        lifted. The pcrepartial documentation gives details of  partial  match-
+        ing.
           PCRE_INFO_OPTIONS
-        Return a copy of the options with which the pattern was  compiled.  The
+        Return  a  copy of the options with which the pattern was compiled. The
-        fourth  argument  should  point to an unsigned long int variable. These
+        fourth argument should point to an unsigned long  int  variable.  These
         option bits are those specified in the call to pcre_compile(), modified
         by any top-level option settings at the start of the pattern itself. In
-        other words, they are the options that will be in force  when  matching
+        other  words,  they are the options that will be in force when matching
-        starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with
+        starts. For example, if the pattern /(?im)abc(?-i)d/ is  compiled  with
-        the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
+        the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,
         and PCRE_EXTENDED.
-        A  pattern  is  automatically  anchored by PCRE if all of its top-level
+        A pattern is automatically anchored by PCRE if  all  of  its  top-level
         alternatives begin with one of the following:
           ^     unless PCRE_MULTILINE is set
-Line 1750 
 INFORMATION ABOUT A PATTERN
+Line 1823 
 INFORMATION ABOUT A PATTERN
           PCRE_INFO_SIZE
-        Return  the  size  of the compiled pattern, that is, the value that was
+        Return the size of the compiled pattern, that is, the  value  that  was
         passed as the argument to pcre_malloc() when PCRE was getting memory in
         which to place the compiled data. The fourth argument should point to a
         size_t variable.
-Line 1758 
 INFORMATION ABOUT A PATTERN
+Line 1831 
 INFORMATION ABOUT A PATTERN
           PCRE_INFO_STUDYSIZE
         Return the size of the data block pointed to by the study_data field in
-        a  pcre_extra  block.  That  is,  it  is  the  value that was passed to
+        a pcre_extra block. That is,  it  is  the  value  that  was  passed  to
         pcre_malloc() when PCRE was getting memory into which to place the data
-        created  by  pcre_study(). The fourth argument should point to a size_t
+        created by pcre_study(). If pcre_extra is NULL, or there  is  no  study
+        data,  zero  is  returned. The fourth argument should point to a size_t
         variable.
-Line 1816 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 1890 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
         The  function pcre_exec() is called to match a subject string against a
         compiled pattern, which is passed in the code argument. If the  pattern
-        has been studied, the result of the study should be passed in the extra
+        was  studied,  the  result  of  the study should be passed in the extra
         argument. This function is the main matching facility of  the  library,
         and it operates in a Perl-like manner. For specialist use there is also
         an alternative matching function, which is described below in the  sec-
-Line 1856 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 1930 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
           unsigned long int match_limit_recursion;
           void *callout_data;
           const unsigned char *tables;
+          unsigned char **mark;
         The  flags  field  is a bitmap that specifies which of the other fields
         are set. The flag bits are:
-Line 1865 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 1940 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
           PCRE_EXTRA_MATCH_LIMIT_RECURSION
           PCRE_EXTRA_CALLOUT_DATA
           PCRE_EXTRA_TABLES
+          PCRE_EXTRA_MARK
         Other flag bits should be set to zero. The study_data field is  set  in
         the  pcre_extra  block  that is returned by pcre_study(), together with
-Line 1875 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 1951 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
         The match_limit field provides a means of preventing PCRE from using up
         a  vast amount of resources when running patterns that are not going to
         match, but which have a very large number  of  possibilities  in  their
-        search  trees.  The  classic  example  is  the  use of nested unlimited
+        search  trees. The classic example is a pattern that uses nested unlim-
-        repeats.
+        ited repeats.
         Internally, PCRE uses a function called match() which it calls  repeat-
         edly  (sometimes  recursively). The limit set by match_limit is imposed
-Line 1909 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 1985 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
         PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the
         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
-        The  pcre_callout  field is used in conjunction with the "callout" fea-
+        The  callout_data  field is used in conjunction with the "callout" fea-
-        ture, which is described in the pcrecallout documentation.
+        ture, and is described in the pcrecallout documentation.
         The tables field  is  used  to  pass  a  character  tables  pointer  to
         pcre_exec();  this overrides the value that is stored with the compiled
-Line 1923 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 1999 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
         address when pcre_exec() is called. See the  pcreprecompile  documenta-
         tion for a discussion of saving compiled patterns for later use.
+        If  PCRE_EXTRA_MARK  is  set in the flags field, the mark field must be
+        set to point to a char * variable. If the pattern  contains  any  back-
+        tracking  control verbs such as (*MARK:NAME), and the execution ends up
+        with a name to pass back, a pointer to the  name  string  (zero  termi-
+        nated)  is  placed  in  the  variable pointed to by the mark field. The
+        names are within the compiled pattern; if you wish  to  retain  such  a
+        name  you must copy it before freeing the memory of a compiled pattern.
+        If there is no name to pass back, the variable pointed to by  the  mark
+        field  set  to NULL. For details of the backtracking control verbs, see
+        the section entitled "Backtracking control" in the pcrepattern documen-
+        tation.
     Option bits for pcre_exec()
         The  unused  bits of the options argument for pcre_exec() must be zero.
         The only bits that may  be  set  are  PCRE_ANCHORED,  PCRE_NEWLINE_xxx,
-        PCRE_NOTBOL,    PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_START_OPTIMIZE,
+        PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,
-        PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and PCRE_PARTIAL_HARD.
+        PCRE_NO_START_OPTIMIZE,  PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,   and
+        PCRE_PARTIAL_HARD.
           PCRE_ANCHORED
-        The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first
+        The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first
-        matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or
+        matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or
-        turned out to be anchored by virtue of its contents, it cannot be  made
+        turned  out to be anchored by virtue of its contents, it cannot be made
         unachored at matching time.
           PCRE_BSR_ANYCRLF
           PCRE_BSR_UNICODE
         These options (which are mutually exclusive) control what the \R escape
-        sequence matches. The choice is either to match only CR, LF,  or  CRLF,
+        sequence  matches.  The choice is either to match only CR, LF, or CRLF,
-        or  to  match  any Unicode newline sequence. These options override the
+        or to match any Unicode newline sequence. These  options  override  the
         choice that was made or defaulted when the pattern was compiled.
           PCRE_NEWLINE_CR
-Line 1951 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 2040 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
           PCRE_NEWLINE_ANYCRLF
           PCRE_NEWLINE_ANY
-        These options override  the  newline  definition  that  was  chosen  or
+        These  options  override  the  newline  definition  that  was chosen or
-        defaulted  when the pattern was compiled. For details, see the descrip-
+        defaulted when the pattern was compiled. For details, see the  descrip-
-        tion of pcre_compile()  above.  During  matching,  the  newline  choice
+        tion  of  pcre_compile()  above.  During  matching,  the newline choice
-        affects  the  behaviour  of the dot, circumflex, and dollar metacharac-
+        affects the behaviour of the dot, circumflex,  and  dollar  metacharac-
-        ters. It may also alter the way the match position is advanced after  a
+        ters.  It may also alter the way the match position is advanced after a
         match failure for an unanchored pattern.
-        When  PCRE_NEWLINE_CRLF,  PCRE_NEWLINE_ANYCRLF,  or PCRE_NEWLINE_ANY is
+        When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is
-        set, and a match attempt for an unanchored pattern fails when the  cur-
+        set,  and a match attempt for an unanchored pattern fails when the cur-
-        rent  position  is  at  a  CRLF  sequence,  and the pattern contains no
+        rent position is at a  CRLF  sequence,  and  the  pattern  contains  no
-        explicit matches for  CR  or  LF  characters,  the  match  position  is
+        explicit  matches  for  CR  or  LF  characters,  the  match position is
         advanced by two characters instead of one, in other words, to after the
         CRLF.
         The above rule is a compromise that makes the most common cases work as
-        expected.  For  example,  if  the  pattern  is .+A (and the PCRE_DOTALL
+        expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL
         option is not set), it does not match the string "\r\nA" because, after
-        failing  at the start, it skips both the CR and the LF before retrying.
+        failing at the start, it skips both the CR and the LF before  retrying.
-        However, the pattern [\r\n]A does match that string,  because  it  con-
+        However,  the  pattern  [\r\n]A does match that string, because it con-
         tains an explicit CR or LF reference, and so advances only by one char-
         acter after the first failure.
         An explicit match for CR of LF is either a literal appearance of one of
-        those  characters,  or  one  of the \r or \n escape sequences. Implicit
+        those characters, or one of the \r or  \n  escape  sequences.  Implicit
-        matches such as [^X] do not count, nor does \s (which includes  CR  and
+        matches  such  as [^X] do not count, nor does \s (which includes CR and
         LF in the characters that it matches).
-        Notwithstanding  the above, anomalous effects may still occur when CRLF
+        Notwithstanding the above, anomalous effects may still occur when  CRLF
         is a valid newline sequence and explicit \r or \n escapes appear in the
         pattern.
           PCRE_NOTBOL
         This option specifies that first character of the subject string is not
-        the beginning of a line, so the  circumflex  metacharacter  should  not
+        the  beginning  of  a  line, so the circumflex metacharacter should not
-        match  before it. Setting this without PCRE_MULTILINE (at compile time)
+        match before it. Setting this without PCRE_MULTILINE (at compile  time)
-        causes circumflex never to match. This option affects only  the  behav-
+        causes  circumflex  never to match. This option affects only the behav-
         iour of the circumflex metacharacter. It does not affect \A.
           PCRE_NOTEOL
         This option specifies that the end of the subject string is not the end
-        of a line, so the dollar metacharacter should not match it nor  (except
+        of  a line, so the dollar metacharacter should not match it nor (except
-        in  multiline mode) a newline immediately before it. Setting this with-
+        in multiline mode) a newline immediately before it. Setting this  with-
         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
-        option  affects only the behaviour of the dollar metacharacter. It does
+        option affects only the behaviour of the dollar metacharacter. It  does
         not affect \Z or \z.
           PCRE_NOTEMPTY
         An empty string is not considered to be a valid match if this option is
-        set.  If  there are alternatives in the pattern, they are tried. If all
+        set. If there are alternatives in the pattern, they are tried.  If  all
-        the alternatives match the empty string, the entire  match  fails.  For
+        the  alternatives  match  the empty string, the entire match fails. For
         example, if the pattern
           a?b?
-        is  applied  to  a string not beginning with "a" or "b", it matches the
+        is applied to a string not beginning with "a" or  "b",  it  matches  an
-        empty string at the start of the subject. With PCRE_NOTEMPTY set,  this
+        empty  string at the start of the subject. With PCRE_NOTEMPTY set, this
         match is not valid, so PCRE searches further into the string for occur-
         rences of "a" or "b".
-        Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-
+          PCRE_NOTEMPTY_ATSTART
-        cial  case  of  a  pattern match of the empty string within its split()
-        function, and when using the /g modifier. It  is  possible  to  emulate
+        This  is  like PCRE_NOTEMPTY, except that an empty string match that is
-        Perl's behaviour after matching a null string by first trying the match
+        not at the start of  the  subject  is  permitted.  If  the  pattern  is
-        again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then
+        anchored, such a match can occur only if the pattern contains \K.
-        if  that  fails by advancing the starting offset (see below) and trying
-        an ordinary match again. There is some code that demonstrates how to do
+        Perl     has    no    direct    equivalent    of    PCRE_NOTEMPTY    or
-        this in the pcredemo sample program.
+        PCRE_NOTEMPTY_ATSTART, but it does make a special  case  of  a  pattern
+        match  of  the empty string within its split() function, and when using
+        the /g modifier. It is  possible  to  emulate  Perl's  behaviour  after
+        matching a null string by first trying the match again at the same off-
+        set with PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED,  and  then  if  that
+        fails, by advancing the starting offset (see below) and trying an ordi-
+        nary match again. There is some code that demonstrates how to  do  this
+        in the pcredemo sample program.
           PCRE_NO_START_OPTIMIZE
-Line 2066 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 2162 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
         returns  PCRE_ERROR_PARTIAL.  Otherwise,  if  PCRE_PARTIAL_SOFT is set,
         matching continues by testing any other alternatives. Only if they  all
         fail  is  PCRE_ERROR_PARTIAL  returned (instead of PCRE_ERROR_NOMATCH).
-        The portion of the string that provided the partial match is set as the
+        The portion of the string that was inspected when the partial match was
-        first  matching  string.  There  is  a  more detailed discussion in the
+        found  is  set  as  the first matching string. There is a more detailed
-        pcrepartial documentation.
+        discussion in the pcrepartial documentation.
     The string to be matched by pcre_exec()
-Line 2155 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 2251 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
         has to get additional memory for use during matching. Thus it  is  usu-
         ally advisable to supply an ovector.
-        The  pcre_info()  function  can  be used to find out how many capturing
+        The pcre_fullinfo() function can be used to find out how many capturing
         subpatterns there are in a compiled  pattern.  The  smallest  size  for
         ovector  that  will allow for n captured substrings, in addition to the
         offsets of the substring matched by the whole pattern, is (n+1)*3.
-Line 2218 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 2314 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
         purpose.  If the call via pcre_malloc() fails, this error is given. The
         memory is automatically freed at the end of matching.
+        This error is also given if pcre_stack_malloc() fails  in  pcre_exec().
+        This  can happen only when PCRE has been compiled with --disable-stack-
+        for-recursion.
           PCRE_ERROR_NOSUBSTRING    (-7)
         This error is used by the pcre_copy_substring(),  pcre_get_substring(),
-Line 2416 
 EXTRACTING CAPTURED SUBSTRINGS BY NAME
+Line 2516 
 EXTRACTING CAPTURED SUBSTRINGS BY NAME
         ate.  NOTE:  If PCRE_DUPNAMES is set and there are duplicate names, the
         behaviour may not be what you want (see the next section).
-        Warning: If the pattern uses the "(?|" feature to set up multiple  sub-
+        Warning: If the pattern uses the (?| feature to set up multiple subpat-
-        patterns  with  the  same  number,  you cannot use names to distinguish
+        terns  with  the  same number, as described in the section on duplicate
-        them, because names are not included in the compiled code. The matching
+        subpattern numbers in the pcrepattern page, you  cannot  use  names  to
-        process uses only numbers.
+        distinguish  the  different subpatterns, because names are not included
+        in the compiled code. The matching process uses only numbers. For  this
+        reason,  the  use of different names for subpatterns of the same number
+        causes an error at compile time.
  DUPLICATE SUBPATTERN NAMES
-Line 2427 
 DUPLICATE SUBPATTERN NAMES
+Line 2530 
 DUPLICATE SUBPATTERN NAMES
         int pcre_get_stringtable_entries(const pcre *code,
              const char *name, char **first, char **last);
-        When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
+        When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for
-        subpatterns are not required to  be  unique.  Normally,  patterns  with
+        subpatterns  are not required to be unique. (Duplicate names are always
-        duplicate  names  are such that in any one match, only one of the named
+        allowed for subpatterns with the same number, created by using the  (?|
-        subpatterns participates. An example is shown in the pcrepattern  docu-
+        feature.  Indeed,  if  such subpatterns are named, they are required to
-        mentation.
+        use the same names.)
-        When    duplicates   are   present,   pcre_copy_named_substring()   and
+        Normally, patterns with duplicate names are such that in any one match,
-        pcre_get_named_substring() return the first substring corresponding  to
+        only  one of the named subpatterns participates. An example is shown in
-        the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
+        the pcrepattern documentation.
-        (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
-        function  returns one of the numbers that are associated with the name,
+        When   duplicates   are   present,   pcre_copy_named_substring()    and
+        pcre_get_named_substring()  return the first substring corresponding to
+        the given name that is set. If  none  are  set,  PCRE_ERROR_NOSUBSTRING
+        (-7)  is  returned;  no  data  is returned. The pcre_get_stringnumber()
+        function returns one of the numbers that are associated with the  name,
         but it is not defined which it is.
-        If you want to get full details of all captured substrings for a  given
+        If  you want to get full details of all captured substrings for a given
-        name,  you  must  use  the pcre_get_stringtable_entries() function. The
+        name, you must use  the  pcre_get_stringtable_entries()  function.  The
         first argument is the compiled pattern, and the second is the name. The
-        third  and  fourth  are  pointers to variables which are updated by the
+        third and fourth are pointers to variables which  are  updated  by  the
         function. After it has run, they point to the first and last entries in
-        the  name-to-number  table  for  the  given  name.  The function itself
+        the name-to-number table  for  the  given  name.  The  function  itself
-        returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
+        returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if
-        there  are none. The format of the table is described above in the sec-
+        there are none. The format of the table is described above in the  sec-
-        tion entitled Information about a  pattern.   Given  all  the  relevant
+        tion  entitled  Information  about  a  pattern.  Given all the relevant
-        entries  for the name, you can extract each of their numbers, and hence
+        entries for the name, you can extract each of their numbers, and  hence
         the captured data, if any.
  FINDING ALL POSSIBLE MATCHES
-        The traditional matching function uses a  similar  algorithm  to  Perl,
+        The  traditional  matching  function  uses a similar algorithm to Perl,
         which stops when it finds the first match, starting at a given point in
-        the subject. If you want to find all possible matches, or  the  longest
+        the  subject.  If you want to find all possible matches, or the longest
-        possible  match,  consider using the alternative matching function (see
+        possible match, consider using the alternative matching  function  (see
-        below) instead. If you cannot use the alternative function,  but  still
+        below)  instead.  If you cannot use the alternative function, but still
-        need  to  find all possible matches, you can kludge it up by making use
+        need to find all possible matches, you can kludge it up by  making  use
         of the callout facility, which is described in the pcrecallout documen-
         tation.
         What you have to do is to insert a callout right at the end of the pat-
-        tern.  When your callout function is called, extract and save the  cur-
+        tern.   When your callout function is called, extract and save the cur-
-        rent  matched  substring.  Then  return  1, which forces pcre_exec() to
+        rent matched substring. Then return  1,  which  forces  pcre_exec()  to
-        backtrack and try other alternatives. Ultimately, when it runs  out  of
+        backtrack  and  try other alternatives. Ultimately, when it runs out of
         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
-Line 2478 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
+Line 2585 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
              int options, int *ovector, int ovecsize,
              int *workspace, int wscount);
-        The  function  pcre_dfa_exec()  is  called  to  match  a subject string
+        The function pcre_dfa_exec()  is  called  to  match  a  subject  string
-        against a compiled pattern, using a matching algorithm that  scans  the
+        against  a  compiled pattern, using a matching algorithm that scans the
-        subject  string  just  once, and does not backtrack. This has different
+        subject string just once, and does not backtrack.  This  has  different
-        characteristics to the normal algorithm, and  is  not  compatible  with
+        characteristics  to  the  normal  algorithm, and is not compatible with
-        Perl.  Some  of the features of PCRE patterns are not supported. Never-
+        Perl. Some of the features of PCRE patterns are not  supported.  Never-
-        theless, there are times when this kind of matching can be useful.  For
+        theless,  there are times when this kind of matching can be useful. For
-        a discussion of the two matching algorithms, see the pcrematching docu-
+        a discussion of the two matching algorithms, and  a  list  of  features
-        mentation.
+        that  pcre_dfa_exec() does not support, see the pcrematching documenta-
+        tion.
         The arguments for the pcre_dfa_exec() function  are  the  same  as  for
         pcre_exec(), plus two extras. The ovector argument is used in a differ-
-Line 2520 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
+Line 2628 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
         The unused bits of the options argument  for  pcre_dfa_exec()  must  be
         zero.  The  only  bits  that  may  be  set are PCRE_ANCHORED, PCRE_NEW-
-        LINE_xxx, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY,  PCRE_NO_UTF8_CHECK,
+        LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
-        PCRE_PARTIAL_HARD,     PCRE_PARTIAL_SOFT,     PCRE_DFA_SHORTEST,    and
+        PCRE_NOTEMPTY_ATSTART, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, PCRE_PAR-
-        PCRE_DFA_RESTART. All but the last four of these are exactly  the  same
+        TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All  but  the  last
-        as for pcre_exec(), so their description is not repeated here.
+        four  of  these  are  exactly  the  same  as  for pcre_exec(), so their
+        description is not repeated here.
           PCRE_PARTIAL_HARD
           PCRE_PARTIAL_SOFT
-        These  have the same general effect as they do for pcre_exec(), but the
+        These have the same general effect as they do for pcre_exec(), but  the
-        details are slightly  different.  When  PCRE_PARTIAL_HARD  is  set  for
+        details  are  slightly  different.  When  PCRE_PARTIAL_HARD  is set for
-        pcre_dfa_exec(),  it  returns PCRE_ERROR_PARTIAL if the end of the sub-
+        pcre_dfa_exec(), it returns PCRE_ERROR_PARTIAL if the end of  the  sub-
-        ject is reached and there is still at least  one  matching  possibility
+        ject  is  reached  and there is still at least one matching possibility
         that requires additional characters. This happens even if some complete
         matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
         code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
-        of the subject is reached, there have been  no  complete  matches,  but
+        of  the  subject  is  reached, there have been no complete matches, but
-        there  is  still  at least one matching possibility. The portion of the
+        there is still at least one matching possibility. The  portion  of  the
-        string that provided the longest partial match  is  set  as  the  first
+        string  that  was inspected when the longest partial match was found is
-        matching string in both cases.
+        set as the first matching string in both cases.
           PCRE_DFA_SHORTEST
-        Setting  the  PCRE_DFA_SHORTEST option causes the matching algorithm to
+        Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to
         stop as soon as it has found one match. Because of the way the alterna-
-        tive  algorithm  works, this is necessarily the shortest possible match
+        tive algorithm works, this is necessarily the shortest  possible  match
         at the first possible matching point in the subject string.
           PCRE_DFA_RESTART
         When pcre_dfa_exec() returns a partial match, it is possible to call it
-        again,  with  additional  subject characters, and have it continue with
+        again, with additional subject characters, and have  it  continue  with
-        the same match. The PCRE_DFA_RESTART option requests this action;  when
+        the  same match. The PCRE_DFA_RESTART option requests this action; when
-        it  is  set,  the workspace and wscount options must reference the same
+        it is set, the workspace and wscount options must  reference  the  same
-        vector as before because data about the match so far is  left  in  them
+        vector  as  before  because data about the match so far is left in them
         after a partial match. There is more discussion of this facility in the
         pcrepartial documentation.
     Successful returns from pcre_dfa_exec()
-        When pcre_dfa_exec() succeeds, it may have matched more than  one  sub-
+        When  pcre_dfa_exec()  succeeds, it may have matched more than one sub-
         string in the subject. Note, however, that all the matches from one run
-        of the function start at the same point in  the  subject.  The  shorter
+        of  the  function  start  at the same point in the subject. The shorter
-        matches  are all initial substrings of the longer matches. For example,
+        matches are all initial substrings of the longer matches. For  example,
         if the pattern
           <.*>
-Line 2577 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
+Line 2686 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
           <something> <something else>
           <something> <something else> <something further>
-        On success, the yield of the function is a number  greater  than  zero,
+        On  success,  the  yield of the function is a number greater than zero,
-        which  is  the  number of matched substrings. The substrings themselves
+        which is the number of matched substrings.  The  substrings  themselves
-        are returned in ovector. Each string uses two elements;  the  first  is
+        are  returned  in  ovector. Each string uses two elements; the first is
-        the  offset  to  the start, and the second is the offset to the end. In
+        the offset to the start, and the second is the offset to  the  end.  In
-        fact, all the strings have the same start  offset.  (Space  could  have
+        fact,  all  the  strings  have the same start offset. (Space could have
-        been  saved by giving this only once, but it was decided to retain some
+        been saved by giving this only once, but it was decided to retain  some
-        compatibility with the way pcre_exec() returns data,  even  though  the
+        compatibility  with  the  way pcre_exec() returns data, even though the
         meaning of the strings is different.)
         The strings are returned in reverse order of length; that is, the long-
-        est matching string is given first. If there were too many  matches  to
+        est  matching  string is given first. If there were too many matches to
-        fit  into ovector, the yield of the function is zero, and the vector is
+        fit into ovector, the yield of the function is zero, and the vector  is
         filled with the longest matches.
     Error returns from pcre_dfa_exec()
-        The pcre_dfa_exec() function returns a negative number when  it  fails.
+        The  pcre_dfa_exec()  function returns a negative number when it fails.
-        Many  of  the  errors  are  the  same as for pcre_exec(), and these are
+        Many of the errors are the same  as  for  pcre_exec(),  and  these  are
-        described above.  There are in addition the following errors  that  are
+        described  above.   There are in addition the following errors that are
         specific to pcre_dfa_exec():
           PCRE_ERROR_DFA_UITEM      (-16)
-        This  return is given if pcre_dfa_exec() encounters an item in the pat-
+        This return is given if pcre_dfa_exec() encounters an item in the  pat-
-        tern that it does not support, for instance, the use of \C  or  a  back
+        tern  that  it  does not support, for instance, the use of \C or a back
         reference.
           PCRE_ERROR_DFA_UCOND      (-17)
-        This  return  is  given  if pcre_dfa_exec() encounters a condition item
+        This return is given if pcre_dfa_exec()  encounters  a  condition  item
-        that uses a back reference for the condition, or a test  for  recursion
+        that  uses  a back reference for the condition, or a test for recursion
         in a specific group. These are not supported.
           PCRE_ERROR_DFA_UMLIMIT    (-18)
-        This  return  is given if pcre_dfa_exec() is called with an extra block
+        This return is given if pcre_dfa_exec() is called with an  extra  block
         that contains a setting of the match_limit field. This is not supported
         (it is meaningless).
           PCRE_ERROR_DFA_WSSIZE     (-19)
-        This  return  is  given  if  pcre_dfa_exec()  runs  out of space in the
+        This return is given if  pcre_dfa_exec()  runs  out  of  space  in  the
         workspace vector.
           PCRE_ERROR_DFA_RECURSE    (-20)
-        When a recursive subpattern is processed, the matching  function  calls
+        When  a  recursive subpattern is processed, the matching function calls
-        itself  recursively,  using  private vectors for ovector and workspace.
+        itself recursively, using private vectors for  ovector  and  workspace.
-        This error is given if the output vector  is  not  large  enough.  This
+        This  error  is  given  if  the output vector is not large enough. This
         should be extremely rare, as a vector of size 1000 is used.
  SEE ALSO
-        pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-
+        pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-
         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
-Line 2644 
 AUTHOR
+Line 2753 
 AUTHOR
  REVISION
-        Last updated: 01 September 2009
+        Last updated: 01 June 2010
-        Copyright (c) 1997-2009 University of Cambridge.
+        Copyright (c) 1997-2010 University of Cambridge.
  ------------------------------------------------------------------------------
  PCRECALLOUT(3)                                                  PCRECALLOUT(3)
-Line 2674 
 PCRE CALLOUTS
+Line 2783 
 PCRE CALLOUTS
           (?C1)abc(?C2)def
-        If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() is
+        If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() or
-        called, PCRE automatically  inserts  callouts,  all  with  number  255,
+        pcre_compile2() is called, PCRE  automatically  inserts  callouts,  all
-        before  each  item in the pattern. For example, if PCRE_AUTO_CALLOUT is
+        with  number  255,  before  each  item  in the pattern. For example, if
-        used with the pattern
+        PCRE_AUTO_CALLOUT is used with the pattern
           A(\d{2}|--)
-Line 2706 
 MISSING CALLOUTS
+Line 2815 
 MISSING CALLOUTS
         ever  start,  and  the  callout is never reached. However, with "abyd",
         though the result is still no match, the callout is obeyed.
-        You can disable these optimizations by passing the  PCRE_NO_START_OPTI-
+        If the pattern is studied, PCRE knows the minimum length of a  matching
-        MIZE  option  to  pcre_exec()  or  pcre_dfa_exec(). This slows down the
+        string,  and will immediately give a "no match" return without actually
-        matching process, but does ensure that callouts  such  as  the  example
+        running a match if the subject is not long enough, or,  for  unanchored
+        patterns, if it has been scanned far enough.
+        You  can disable these optimizations by passing the PCRE_NO_START_OPTI-
+        MIZE option to pcre_exec() or  pcre_dfa_exec().  This  slows  down  the
+        matching  process,  but  does  ensure that callouts such as the example
         above are obeyed.
  THE CALLOUT INTERFACE
-        During  matching, when PCRE reaches a callout point, the external func-
+        During matching, when PCRE reaches a callout point, the external  func-
-        tion defined by pcre_callout is called (if it is set). This applies  to
+        tion  defined by pcre_callout is called (if it is set). This applies to
-        both  the  pcre_exec()  and the pcre_dfa_exec() matching functions. The
+        both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The
-        only argument to the callout function is a pointer  to  a  pcre_callout
+        only  argument  to  the callout function is a pointer to a pcre_callout
         block. This structure contains the following fields:
           int          version;
-Line 2733 
 THE CALLOUT INTERFACE
+Line 2847 
 THE CALLOUT INTERFACE
           int          pattern_position;
           int          next_item_length;
-        The  version  field  is an integer containing the version number of the
+        The version field is an integer containing the version  number  of  the
-        block format. The initial version was 0; the current version is 1.  The
+        block  format. The initial version was 0; the current version is 1. The
-        version  number  will  change  again in future if additional fields are
+        version number will change again in future  if  additional  fields  are
         added, but the intention is never to remove any of the existing fields.
-        The callout_number field contains the number of the  callout,  as  com-
+        The  callout_number  field  contains the number of the callout, as com-
-        piled  into  the pattern (that is, the number after ?C for manual call-
+        piled into the pattern (that is, the number after ?C for  manual  call-
         outs, and 255 for automatically generated callouts).
-        The offset_vector field is a pointer to the vector of offsets that  was
+        The  offset_vector field is a pointer to the vector of offsets that was
-        passed   by   the   caller  to  pcre_exec()  or  pcre_dfa_exec().  When
+        passed  by  the  caller  to  pcre_exec()   or   pcre_dfa_exec().   When
-        pcre_exec() is used, the contents can be inspected in order to  extract
+        pcre_exec()  is used, the contents can be inspected in order to extract
-        substrings  that  have  been  matched  so  far,  in the same way as for
+        substrings that have been matched so  far,  in  the  same  way  as  for
-        extracting substrings after a match has completed. For  pcre_dfa_exec()
+        extracting  substrings after a match has completed. For pcre_dfa_exec()
         this field is not useful.
         The subject and subject_length fields contain copies of the values that
         were passed to pcre_exec().
-        The start_match field normally contains the offset within  the  subject
+        The  start_match  field normally contains the offset within the subject
-        at  which  the  current  match  attempt started. However, if the escape
+        at which the current match attempt  started.  However,  if  the  escape
-        sequence \K has been encountered, this value is changed to reflect  the
+        sequence  \K has been encountered, this value is changed to reflect the
-        modified  starting  point.  If the pattern is not anchored, the callout
+        modified starting point. If the pattern is not  anchored,  the  callout
         function may be called several times from the same point in the pattern
         for different starting points in the subject.
-        The  current_position  field  contains the offset within the subject of
+        The current_position field contains the offset within  the  subject  of
         the current match pointer.
-        When the pcre_exec() function is used, the capture_top  field  contains
+        When  the  pcre_exec() function is used, the capture_top field contains
-        one  more than the number of the highest numbered captured substring so
+        one more than the number of the highest numbered captured substring  so
-        far. If no substrings have been captured, the value of  capture_top  is
+        far.  If  no substrings have been captured, the value of capture_top is
-        one.  This  is always the case when pcre_dfa_exec() is used, because it
+        one. This is always the case when pcre_dfa_exec() is used,  because  it
         does not support captured substrings.
-        The capture_last field contains the number of the  most  recently  cap-
+        The  capture_last  field  contains the number of the most recently cap-
-        tured  substring. If no substrings have been captured, its value is -1.
+        tured substring. If no substrings have been captured, its value is  -1.
         This is always the case when pcre_dfa_exec() is used.
-        The callout_data field contains a value that is passed  to  pcre_exec()
+        The  callout_data  field contains a value that is passed to pcre_exec()
-        or  pcre_dfa_exec() specifically so that it can be passed back in call-
+        or pcre_dfa_exec() specifically so that it can be passed back in  call-
-        outs. It is passed in the pcre_callout field  of  the  pcre_extra  data
+        outs.  It  is  passed  in the pcre_callout field of the pcre_extra data
-        structure.  If  no such data was passed, the value of callout_data in a
+        structure. If no such data was passed, the value of callout_data  in  a
-        pcre_callout block is NULL. There is a description  of  the  pcre_extra
+        pcre_callout  block  is  NULL. There is a description of the pcre_extra
         structure in the pcreapi documentation.
-        The  pattern_position field is present from version 1 of the pcre_call-
+        The pattern_position field is present from version 1 of the  pcre_call-
         out structure. It contains the offset to the next item to be matched in
         the pattern string.
-        The  next_item_length field is present from version 1 of the pcre_call-
+        The next_item_length field is present from version 1 of the  pcre_call-
         out structure. It contains the length of the next item to be matched in
-        the  pattern  string. When the callout immediately precedes an alterna-
+        the pattern string. When the callout immediately precedes  an  alterna-
-        tion bar, a closing parenthesis, or the end of the pattern, the  length
+        tion  bar, a closing parenthesis, or the end of the pattern, the length
-        is  zero.  When the callout precedes an opening parenthesis, the length
+        is zero. When the callout precedes an opening parenthesis,  the  length
         is that of the entire subpattern.
-        The pattern_position and next_item_length fields are intended  to  help
+        The  pattern_position  and next_item_length fields are intended to help
-        in  distinguishing between different automatic callouts, which all have
+        in distinguishing between different automatic callouts, which all  have
         the same callout number. However, they are set for all callouts.
  RETURN VALUES
-        The external callout function returns an integer to PCRE. If the  value
+        The  external callout function returns an integer to PCRE. If the value
-        is  zero,  matching  proceeds  as  normal. If the value is greater than
+        is zero, matching proceeds as normal. If  the  value  is  greater  than
-        zero, matching fails at the current point, but  the  testing  of  other
+        zero,  matching  fails  at  the current point, but the testing of other
         matching possibilities goes ahead, just as if a lookahead assertion had
-        failed. If the value is less than zero, the  match  is  abandoned,  and
+        failed.  If  the  value  is less than zero, the match is abandoned, and
-        pcre_exec() (or pcre_dfa_exec()) returns the negative value.
+        pcre_exec() or pcre_dfa_exec() returns the negative value.
-        Negative   values   should   normally   be   chosen  from  the  set  of
+        Negative  values  should  normally  be   chosen   from   the   set   of
         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
-        dard  "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT is
+        dard "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT  is
-        reserved for use by callout functions; it will never be  used  by  PCRE
+        reserved  for  use  by callout functions; it will never be used by PCRE
         itself.
-Line 2820 
 AUTHOR
+Line 2934 
 AUTHOR
  REVISION
-        Last updated: 15 March 2009
+        Last updated: 29 September 2009
         Copyright (c) 1997-2009 University of Cambridge.
  ------------------------------------------------------------------------------
  PCRECOMPAT(3)                                                    PCRECOMPAT(3)
-Line 2835 
 NAME
+Line 2949 
 NAME
  DIFFERENCES BETWEEN PCRE AND PERL
         This  document describes the differences in the ways that PCRE and Perl
-        handle regular expressions. The differences described here  are  mainly
+        handle regular expressions. The differences  described  here  are  with
-        with  respect  to  Perl 5.8, though PCRE versions 7.0 and later contain
+        respect to Perl 5.10/5.11.
-        some features that are in Perl 5.10.
-. PCRE has only a subset of Perl's UTF-8 and Unicode support.  Details
+.  PCRE has only a subset of Perl's UTF-8 and Unicode support. Details
-        of  what  it does have are given in the section on UTF-8 support in the
+        of what it does have are given in the section on UTF-8 support  in  the
         main pcre page.
 . PCRE does not allow repeat quantifiers on lookahead assertions. Perl
-        permits  them,  but they do not mean what you might think. For example,
+        permits them, but they do not mean what you might think.  For  example,
         (?!a){3} does not assert that the next three characters are not "a". It
         just asserts that the next character is not "a" three times.
-.  Capturing  subpatterns  that occur inside negative lookahead asser-
+. Capturing subpatterns that occur inside  negative  lookahead  asser-
-        tions are counted, but their entries in the offsets  vector  are  never
+        tions  are  counted,  but their entries in the offsets vector are never
-        set.  Perl sets its numerical variables from any such patterns that are
+        set. Perl sets its numerical variables from any such patterns that  are
         matched before the assertion fails to match something (thereby succeed-
-        ing),  but  only  if the negative lookahead assertion contains just one
+        ing), but only if the negative lookahead assertion  contains  just  one
         branch.
-. Though binary zero characters are supported in the  subject  string,
+.  Though  binary zero characters are supported in the subject string,
         they are not allowed in a pattern string because it is passed as a nor-
         mal C string, terminated by zero. The escape sequence \0 can be used in
         the pattern to represent a binary zero.
-.  The  following Perl escape sequences are not supported: \l, \u, \L,
+. The following Perl escape sequences are not supported: \l,  \u,  \L,
         \U, and \N. In fact these are implemented by Perl's general string-han-
-        dling  and are not part of its pattern matching engine. If any of these
+        dling and are not part of its pattern matching engine. If any of  these
         are encountered by PCRE, an error is generated.
-. The Perl escape sequences \p, \P, and \X are supported only if  PCRE
+.  The Perl escape sequences \p, \P, and \X are supported only if PCRE
-        is  built  with Unicode character property support. The properties that
+        is built with Unicode character property support. The  properties  that
-        can be tested with \p and \P are limited to the general category  prop-
+        can  be tested with \p and \P are limited to the general category prop-
-        erties  such  as  Lu and Nd, script names such as Greek or Han, and the
+        erties such as Lu and Nd, script names such as Greek or  Han,  and  the
-        derived properties Any and L&.
+        derived  properties  Any  and  L&. PCRE does support the Cs (surrogate)
+        property, which Perl does not; the  Perl  documentation  says  "Because
+        Perl hides the need for the user to understand the internal representa-
+        tion of Unicode characters, there is no need to implement the  somewhat
+        messy concept of surrogates."
 . PCRE does support the \Q...\E escape for quoting substrings. Charac-
-        ters  in  between  are  treated as literals. This is slightly different
+        ters in between are treated as literals.  This  is  slightly  different
-        from Perl in that $ and @ are  also  handled  as  literals  inside  the
+        from  Perl  in  that  $  and  @ are also handled as literals inside the
-        quotes.  In Perl, they cause variable interpolation (but of course PCRE
+        quotes. In Perl, they cause variable interpolation (but of course  PCRE
         does not have variables). Note the following examples:
             Pattern            PCRE matches      Perl matches
-Line 2884 
 DIFFERENCES BETWEEN PCRE AND PERL
+Line 3001 
 DIFFERENCES BETWEEN PCRE AND PERL
             \Qabc\$xyz\E       abc\$xyz          abc\$xyz
             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz
-        The \Q...\E sequence is recognized both inside  and  outside  character
+        The  \Q...\E  sequence  is recognized both inside and outside character
         classes.
 . Fairly obviously, PCRE does not support the (?{code}) and (??{code})
-        constructions. However, there is support for recursive  patterns.  This
+        constructions.  However,  there is support for recursive patterns. This
-        is  not available in Perl 5.8, but will be in Perl 5.10. Also, the PCRE
+        is not available in Perl 5.8, but it is in Perl 5.10.  Also,  the  PCRE
-        "callout" feature allows an external function to be called during  pat-
+        "callout"  feature allows an external function to be called during pat-
         tern matching. See the pcrecallout documentation for details.
-.  Subpatterns  that  are  called  recursively or as "subroutines" are
+. Subpatterns that are called  recursively  or  as  "subroutines"  are
-        always treated as atomic groups in  PCRE.  This  is  like  Python,  but
+        always  treated  as  atomic  groups  in  PCRE. This is like Python, but
-        unlike Perl.
+        unlike Perl. There is a discussion of an example that explains this  in
+        more  detail  in  the section on recursion differences from Perl in the
-.  There are some differences that are concerned with the settings of
+        pcrepattern page.
-        captured strings when part of  a  pattern  is  repeated.  For  example,
-        matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2
+. There are some differences that are concerned with the settings  of
+        captured  strings  when  part  of  a  pattern is repeated. For example,
+        matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2
         unset, but in PCRE it is set to "b".
-.  PCRE  does  support  Perl  5.10's  backtracking  verbs  (*ACCEPT),
+.  PCRE's handling of duplicate subpattern numbers and duplicate sub-
-        (*FAIL),  (*F),  (*COMMIT), (*PRUNE), (*SKIP), and (*THEN), but only in
+        pattern names is not as general as Perl's. This is a consequence of the
-        the forms without an  argument.  PCRE  does  not  support  (*MARK).  If
+        fact the PCRE works internally just with numbers, using an external ta-
-        (*ACCEPT)  is within capturing parentheses, PCRE does not set that cap-
+        ble to translate between numbers and names. In  particular,  a  pattern
-        ture group; this is different to Perl.
+        such  as  (?|(?<a>A)|(?<b)B),  where the two capturing parentheses have
+        the same number but different names, is not supported,  and  causes  an
+        error  at compile time. If it were allowed, it would not be possible to
+        distinguish which parentheses matched, because both names map  to  cap-
+        turing subpattern number 1. To avoid this confusing situation, an error
+        is given at compile time.
 . PCRE provides some extensions to the Perl regular expression facil-
-        ities.   Perl  5.10  will  include new features that are not in earlier
+        ities.   Perl  5.10  includes new features that are not in earlier ver-
-        versions, some of which (such as named parentheses) have been  in  PCRE
+        sions of Perl, some of which (such as named parentheses) have  been  in
-        for some time. This list is with respect to Perl 5.10:
+        PCRE for some time. This list is with respect to Perl 5.10:
-        (a)  Although  lookbehind  assertions  must match fixed length strings,
+        (a)  Although  lookbehind  assertions  in  PCRE must match fixed length
-        each alternative branch of a lookbehind assertion can match a different
+        strings, each alternative branch of a lookbehind assertion can match  a
-        length of string. Perl requires them all to have the same length.
+        different  length  of  string.  Perl requires them all to have the same
+        length.
-        (b)  If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $
+        (b) If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the  $
         meta-character matches only at the very end of the string.
         (c) If PCRE_EXTRA is set, a backslash followed by a letter with no spe-
         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
         ignored.  (Perl can be made to issue a warning.)
-        (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-
+        (d)  If  PCRE_UNGREEDY is set, the greediness of the repetition quanti-
         fiers is inverted, that is, by default they are not greedy, but if fol-
         lowed by a question mark they are.
         (e) PCRE_ANCHORED can be used at matching time to force a pattern to be
         tried only at the first matching position in the subject string.
-        (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-
+        (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
-        TURE options for pcre_exec() have no Perl equivalents.
+        and  PCRE_NO_AUTO_CAPTURE  options for pcre_exec() have no Perl equiva-
+        lents.
         (g) The \R escape sequence can be restricted to match only CR,  LF,  or
         CRLF by the PCRE_BSR_ANYCRLF option.
-Line 2961 
 AUTHOR
+Line 3087 
 AUTHOR
  REVISION
-        Last updated: 25 August 2009
+        Last updated: 12 May 2010
-        Copyright (c) 1997-2009 University of Cambridge.
+        Copyright (c) 1997-2010 University of Cambridge.
  ------------------------------------------------------------------------------
  PCREPATTERN(3)                                                  PCREPATTERN(3)
-Line 2992 
 PCRE REGULAR EXPRESSION DETAILS
+Line 3118 
 PCRE REGULAR EXPRESSION DETAILS
         The original operation of PCRE was on strings of  one-byte  characters.
         However,  there is now also support for UTF-8 character strings. To use
-        this, you must build PCRE to  include  UTF-8  support,  and  then  call
+        this, PCRE must be built to include UTF-8 support, and  you  must  call
-        pcre_compile()  with  the  PCRE_UTF8  option.  There  is also a special
+        pcre_compile()  or  pcre_compile2() with the PCRE_UTF8 option. There is
-        sequence that can be given at the start of a pattern:
+        also a special sequence that can be given at the start of a pattern:
           (*UTF8)
-Line 3004 
 PCRE REGULAR EXPRESSION DETAILS
+Line 3130 
 PCRE REGULAR EXPRESSION DETAILS
         below.  There  is  also  a  summary of UTF-8 features in the section on
         UTF-8 support in the main pcre page.
+        Another special sequence that may appear at the start of a  pattern  or
+        in combination with (*UTF8) is:
+          (*UCP)
+        This  has  the  same  effect  as setting the PCRE_UCP option: it causes
+        sequences such as \d and \w to  use  Unicode  properties  to  determine
+        character types, instead of recognizing only characters with codes less
+        than 128 via a lookup table.
         The remainder of this document discusses the  patterns  that  are  sup-
         ported  by  PCRE when its main matching function, pcre_exec(), is used.
         From  release  6.0,   PCRE   offers   a   second   matching   function,
-Line 3032 
 NEWLINE CONVENTIONS
+Line 3168 
 NEWLINE CONVENTIONS
           (*ANYCRLF)   any of the three above
           (*ANY)       all Unicode newline sequences
-        These override the default and the options given to pcre_compile(). For
+        These  override  the default and the options given to pcre_compile() or
-        example, on a Unix system where LF is the default newline sequence, the
+        pcre_compile2(). For example, on a Unix system where LF is the  default
-        pattern
+        newline sequence, the pattern
           (*CR)a.b
-Line 3044 
 NEWLINE CONVENTIONS
+Line 3180 
 NEWLINE CONVENTIONS
         and that they must be in upper case.  If  more  than  one  of  them  is
         present, the last one is used.
-        The  newline  convention  does  not  affect what the \R escape sequence
+        The  newline convention affects the interpretation of the dot metachar-
-        matches. By default, this is any Unicode  newline  sequence,  for  Perl
+        acter when PCRE_DOTALL is not set, and also the behaviour of  \N.  How-
-        compatibility.  However, this can be changed; see the description of \R
+        ever,  it  does  not  affect  what  the  \R escape sequence matches. By
-        in the section entitled "Newline sequences" below. A change of \R  set-
+        default, this is any Unicode newline sequence, for Perl  compatibility.
-        ting can be combined with a change of newline convention.
+        However,  this can be changed; see the description of \R in the section
+        entitled "Newline sequences" below. A change of \R setting can be  com-
+        bined with a change of newline convention.
  CHARACTERS AND METACHARACTERS
-Line 3151 
 BACKSLASH
+Line 3289 
 BACKSLASH
         acters  in patterns in a visible manner. There is no restriction on the
         appearance of non-printing characters, apart from the binary zero  that
         terminates  a  pattern,  but  when  a pattern is being prepared by text
-        editing, it is usually easier  to  use  one  of  the  following  escape
+        editing, it is  often  easier  to  use  one  of  the  following  escape
         sequences than the binary character it represents:
           \a        alarm, that is, the BEL character (hex 07)
-Line 3161 
 BACKSLASH
+Line 3299 
 BACKSLASH
           \n        linefeed (hex 0A)
           \r        carriage return (hex 0D)
           \t        tab (hex 09)
-          \ddd      character with octal code ddd, or backreference
+          \ddd      character with octal code ddd, or back reference
           \xhh      character with hex code hh
           \x{hhh..} character with hex code hhh..
-Line 3230 
 BACKSLASH
+Line 3368 
 BACKSLASH
         All the sequences that define a single character value can be used both
         inside  and  outside character classes. In addition, inside a character
         class, the sequence \b is interpreted as the backspace  character  (hex
-),  and the sequences \R and \X are interpreted as the characters "R"
+).  The sequences \B, \N, \R, and \X are not special inside a charac-
-        and "X", respectively. Outside a character class, these sequences  have
+        ter class. Like any  other  unrecognized  escape  sequences,  they  are
-        different meanings (see below).
+        treated  as  the  literal characters "B", "N", "R", and "X" by default,
+        but cause an error if the PCRE_EXTRA option is set. Outside a character
+        class, these sequences have different meanings.
     Absolute and relative back references
-Line 3252 
 BACKSLASH
+Line 3392 
 BACKSLASH
     Generic character types
-        Another use of backslash is for specifying generic character types. The
+        Another use of backslash is for specifying generic character types:
-        following are always recognized:
           \d     any decimal digit
           \D     any character that is not a decimal digit
-Line 3266 
 BACKSLASH
+Line 3405 
 BACKSLASH
           \w     any "word" character
           \W     any "non-word" character
-        Each pair of escape sequences partitions the complete set of characters
+        There is also the single sequence \N, which matches a non-newline char-
-        into  two disjoint sets. Any given character matches one, and only one,
+        acter.  This is the same as the "." metacharacter when  PCRE_DOTALL  is
-        of each pair.
+        not set.
-        These character type sequences can appear both inside and outside char-
+        Each  pair of lower and upper case escape sequences partitions the com-
-        acter  classes.  They each match one character of the appropriate type.
+        plete set of characters into two disjoint  sets.  Any  given  character
-        If the current matching point is at the end of the subject string,  all
+        matches  one, and only one, of each pair. The sequences can appear both
-        of them fail, since there is no character to match.
+        inside and outside character classes. They each match one character  of
+        the  appropriate  type.  If the current matching point is at the end of
+        the subject string, all of them fail, because there is no character  to
+        match.
         For  compatibility  with Perl, \s does not match the VT character (code
 ).  This makes it different from the the POSIX "space" class. The  \s
-Line 3281 
 BACKSLASH
+Line 3423 
 BACKSLASH
         "use locale;" is included in a Perl script, \s may match the VT charac-
         ter. In PCRE, it never does.
-        In  UTF-8 mode, characters with values greater than 128 never match \d,
+        A  "word"  character is an underscore or any character that is a letter
-        \s, or \w, and always match \D, \S, and \W. This is true even when Uni-
+        or digit.  By default, the definition of letters  and  digits  is  con-
-        code  character  property  support is available. These sequences retain
+        trolled  by PCRE's low-valued character tables, and may vary if locale-
-        their original meanings from before UTF-8 support was available, mainly
+        specific matching is taking place (see "Locale support" in the  pcreapi
-        for  efficiency  reasons. Note that this also affects \b, because it is
+        page).  For  example,  in  a French locale such as "fr_FR" in Unix-like
-        defined in terms of \w and \W.
+        systems, or "french" in Windows, some character codes greater than  128
+        are  used  for  accented letters, and these are then matched by \w. The
+        use of locales with Unicode is discouraged.
+        By default, in UTF-8 mode, characters  with  values  greater  than  128
+        never  match  \d,  \s,  or  \w,  and always match \D, \S, and \W. These
+        sequences retain their original meanings from before UTF-8 support  was
+        available,  mainly for efficiency reasons. However, if PCRE is compiled
+        with Unicode property support, and the PCRE_UCP option is set, the  be-
+        haviour  is  changed  so  that Unicode properties are used to determine
+        character types, as follows:
+          \d  any character that \p{Nd} matches (decimal digit)
+          \s  any character that \p{Z} matches, plus HT, LF, FF, CR
+          \w  any character that \p{L} or \p{N} matches, plus underscore
+        The upper case escapes match the inverse sets of characters. Note  that
+        \d  matches  only decimal digits, whereas \w matches any Unicode digit,
+        as well as any Unicode letter, and underscore. Note also that  PCRE_UCP
+        affects  \b,  and  \B  because  they are defined in terms of \w and \W.
+        Matching these sequences is noticeably slower when PCRE_UCP is set.
         The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to
-        the  other  sequences, these do match certain high-valued codepoints in
+        the  other  sequences,  which  match  only ASCII characters by default,
-        UTF-8 mode.  The horizontal space characters are:
+        these always  match  certain  high-valued  codepoints  in  UTF-8  mode,
+        whether or not PCRE_UCP is set. The horizontal space characters are:
           U+0009     Horizontal tab
           U+0020     Space
-Line 3322 
 BACKSLASH
+Line 3485 
 BACKSLASH
           U+2028     Line separator
           U+2029     Paragraph separator
-        A "word" character is an underscore or any character less than 256 that
-        is  a  letter  or  digit.  The definition of letters and digits is con-
-        trolled by PCRE's low-valued character tables, and may vary if  locale-
-        specific  matching is taking place (see "Locale support" in the pcreapi
-        page). For example, in a French locale such  as  "fr_FR"  in  Unix-like
-        systems,  or "french" in Windows, some character codes greater than 128
-        are used for accented letters, and these are matched by \w. The use  of
-        locales with Unicode is discouraged.
     Newline sequences
         Outside  a  character class, by default, the escape sequence \R matches
-Line 3363 
 BACKSLASH
+Line 3517 
 BACKSLASH
           (*BSR_ANYCRLF)   CR, LF, or CRLF only
           (*BSR_UNICODE)   any Unicode newline sequence
-        These override the default and the options given to pcre_compile(), but
+        These override the default and the options given to  pcre_compile()  or
-        they can be overridden by options given to pcre_exec(). Note that these
+        pcre_compile2(),  but  they  can  be  overridden  by  options  given to
-        special settings, which are not Perl-compatible, are recognized only at
+        pcre_exec() or pcre_dfa_exec(). Note that these special settings, which
-        the  very  start  of a pattern, and that they must be in upper case. If
+        are  not  Perl-compatible,  are  recognized only at the very start of a
-        more than one of them is present, the last one is  used.  They  can  be
+        pattern, and that they must be in upper case. If more than one of  them
-        combined  with  a  change of newline convention, for example, a pattern
+        is present, the last one is used. They can be combined with a change of
-        can start with:
+        newline convention; for example, a pattern can start with:
           (*ANY)(*BSR_ANYCRLF)
-        Inside a character class, \R matches the letter "R".
+        They can also be combined with the (*UTF8) or (*UCP) special sequences.
+        Inside  a  character  class,  \R  is  treated as an unrecognized escape
+        sequence, and so matches the letter "R" by default, but causes an error
+        if PCRE_EXTRA is set.
     Unicode character properties
         When PCRE is built with Unicode character property support, three addi-
-        tional  escape sequences that match characters with specific properties
+        tional escape sequences that match characters with specific  properties
-        are available.  When not in UTF-8 mode, these sequences are  of  course
+        are  available.   When not in UTF-8 mode, these sequences are of course
-        limited  to  testing characters whose codepoints are less than 256, but
+        limited to testing characters whose codepoints are less than  256,  but
         they do work in this mode.  The extra escape sequences are:
           \p{xx}   a character with the xx property
           \P{xx}   a character without the xx property
           \X       an extended Unicode sequence
-        The property names represented by xx above are limited to  the  Unicode
+        The  property  names represented by xx above are limited to the Unicode
-        script names, the general category properties, and "Any", which matches
+        script names, the general category properties, "Any", which matches any
-        any character (including newline). Other properties such as "InMusical-
+        character   (including  newline),  and  some  special  PCRE  properties
-        Symbols"  are  not  currently supported by PCRE. Note that \P{Any} does
+        (described in the next section).  Other Perl properties such as  "InMu-
-        not match any characters, so always causes a match failure.
+        sicalSymbols"  are  not  currently supported by PCRE. Note that \P{Any}
+        does not match any characters, so always causes a match failure.
         Sets of Unicode characters are defined as belonging to certain scripts.
         A  character from one of these sets can be matched using a script name.
-Line 3403 
 BACKSLASH
+Line 3561 
 BACKSLASH
         Those that are not part of an identified script are lumped together  as
         "Common". The current list of scripts is:
-        Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,
+        Arabic, Armenian, Avestan, Balinese, Bamum, Bengali, Bopomofo, Braille,
-        Buhid,  Canadian_Aboriginal,  Cherokee,  Common,   Coptic,   Cuneiform,
+        Buginese, Buhid, Canadian_Aboriginal, Carian, Cham,  Cherokee,  Common,
-        Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,
+        Coptic,   Cuneiform,  Cypriot,  Cyrillic,  Deseret,  Devanagari,  Egyp-
-        Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew,  Hira-
+        tian_Hieroglyphs,  Ethiopic,  Georgian,  Glagolitic,   Gothic,   Greek,
-        gana,  Inherited,  Kannada,  Katakana,  Kharoshthi,  Khmer, Lao, Latin,
+        Gujarati,  Gurmukhi,  Han,  Hangul,  Hanunoo,  Hebrew,  Hiragana, Impe-
-        Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,
+        rial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscriptional_Parthian,
-        Ogham,  Old_Italic,  Old_Persian, Oriya, Osmanya, Phags_Pa, Phoenician,
+        Javanese,  Kaithi, Kannada, Katakana, Kayah_Li, Kharoshthi, Khmer, Lao,
-        Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,
+        Latin,  Lepcha,  Limbu,  Linear_B,  Lisu,  Lycian,  Lydian,  Malayalam,
-        Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.
+        Meetei_Mayek,  Mongolian, Myanmar, New_Tai_Lue, Nko, Ogham, Old_Italic,
+        Old_Persian, Old_South_Arabian, Old_Turkic, Ol_Chiki,  Oriya,  Osmanya,
-        Each  character has exactly one general category property, specified by
+        Phags_Pa,  Phoenician,  Rejang,  Runic, Samaritan, Saurashtra, Shavian,
-        a two-letter abbreviation. For compatibility with Perl, negation can be
+        Sinhala, Sundanese, Syloti_Nagri, Syriac,  Tagalog,  Tagbanwa,  Tai_Le,
-        specified  by  including a circumflex between the opening brace and the
+        Tai_Tham,  Tai_Viet,  Tamil,  Telugu,  Thaana, Thai, Tibetan, Tifinagh,
-        property name. For example, \p{^Lu} is the same as \P{Lu}.
+        Ugaritic, Vai, Yi.
+        Each character has exactly one Unicode general category property, spec-
+        ified  by a two-letter abbreviation. For compatibility with Perl, nega-
+        tion can be specified by including a  circumflex  between  the  opening
+        brace  and  the  property  name.  For  example,  \p{^Lu} is the same as
+        \P{Lu}.
         If only one letter is specified with \p or \P, it includes all the gen-
         eral  category properties that start with that letter. In this case, in
-Line 3480 
 BACKSLASH
+Line 3644 
 BACKSLASH
         U+D800 to U+DFFF. Such characters are not valid in UTF-8  strings  (see
         RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-
         ing has been turned off (see the discussion  of  PCRE_NO_UTF8_CHECK  in
-        the pcreapi page).
+        the pcreapi page). Perl does not support the Cs property.
-        The  long  synonyms  for  these  properties that Perl supports (such as
+        The  long  synonyms  for  property  names  that  Perl supports (such as
         \p{Letter}) are not supported by PCRE, nor is it  permitted  to  prefix
         any of these properties with "Is".
-Line 3508 
 BACKSLASH
+Line 3672 
 BACKSLASH
         Matching characters by Unicode property is not fast, because  PCRE  has
         to  search  a  structure  that  contains data for over fifteen thousand
         characters. That is why the traditional escape sequences such as \d and
-        \w do not use Unicode properties in PCRE.
+        \w  do  not  use  Unicode properties in PCRE by default, though you can
+        make them do so by setting the PCRE_UCP option for pcre_compile() or by
+        starting the pattern with (*UCP).
+    PCRE's additional properties
+        As  well  as  the standard Unicode properties described in the previous
+        section, PCRE supports four more that make it possible to convert  tra-
+        ditional escape sequences such as \w and \s and POSIX character classes
+        to use Unicode properties. PCRE uses these non-standard, non-Perl prop-
+        erties internally when PCRE_UCP is set. They are:
+          Xan   Any alphanumeric character
+          Xps   Any POSIX space character
+          Xsp   Any Perl space character
+          Xwd   Any Perl "word" character
+        Xan  matches  characters that have either the L (letter) or the N (num-
+        ber) property. Xps matches the characters tab, linefeed, vertical  tab,
+        formfeed,  or  carriage  return, and any other character that has the Z
+        (separator) property.  Xsp is the same as Xps, except that vertical tab
+        is excluded. Xwd matches the same characters as Xan, plus underscore.
     Resetting the match start
-Line 3529 
 BACKSLASH
+Line 3714 
 BACKSLASH
         matches "foobar", the first substring is still set to "foo".
+        Perl documents that the use  of  \K  within  assertions  is  "not  well
+        defined".  In  PCRE,  \K  is  acted upon when it occurs inside positive
+        assertions, but is ignored in negative assertions.
     Simple assertions
         The final use of backslash is for certain simple assertions. An  asser-
-Line 3545 
 BACKSLASH
+Line 3734 
 BACKSLASH
           \z     matches only at the end of the subject
           \G     matches at the first matching position in the subject
-        These assertions may not appear in character classes (but note that  \b
+        Inside a character class, \b has a different meaning;  it  matches  the
-        has a different meaning, namely the backspace character, inside a char-
+        backspace  character.  If  any  other  of these assertions appears in a
-        acter class).
+        character class, by default it matches the corresponding literal  char-
+        acter  (for  example,  \B  matches  the  letter  B).  However,  if  the
-        A word boundary is a position in the subject string where  the  current
+        PCRE_EXTRA option is set, an "invalid escape sequence" error is  gener-
-        character  and  the previous character do not both match \w or \W (i.e.
+        ated instead.
-        one matches \w and the other matches \W), or the start or  end  of  the
-        string if the first or last character matches \w, respectively.
+        A  word  boundary is a position in the subject string where the current
+        character and the previous character do not both match \w or  \W  (i.e.
+        one  matches  \w  and the other matches \W), or the start or end of the
+        string if the first or last  character  matches  \w,  respectively.  In
+        UTF-8  mode,  the  meanings  of \w and \W can be changed by setting the
+        PCRE_UCP option. When this is done, it also affects \b and \B.  Neither
+        PCRE  nor  Perl has a separate "start of word" or "end of word" metase-
+        quence. However, whatever follows \b normally determines which  it  is.
+        For example, the fragment \ba matches "a" at the start of a word.
         The  \A,  \Z,  and \z assertions differ from the traditional circumflex
         and dollar (described in the next section) in that they only ever match
-Line 3635 
 CIRCUMFLEX AND DOLLAR
+Line 3832 
 CIRCUMFLEX AND DOLLAR
         set.
- FULL STOP (PERIOD, DOT)
+ FULL STOP (PERIOD, DOT) AND \N
         Outside a character class, a dot in the pattern matches any one charac-
         ter  in  the subject string except (by default) a character that signi-
-Line 3658 
 FULL STOP (PERIOD, DOT)
+Line 3855 
 FULL STOP (PERIOD, DOT)
         flex and dollar, the only relationship being  that  they  both  involve
         newlines. Dot has no special meaning in a character class.
+        The escape sequence \N always behaves as a dot does when PCRE_DOTALL is
+        not set. In other words, it matches any one character except  one  that
+        signifies the end of a line.
  MATCHING A SINGLE BYTE
-Line 3678 
 SQUARE BRACKETS AND CHARACTER CLASSES
+Line 3879 
 SQUARE BRACKETS AND CHARACTER CLASSES
         An opening square bracket introduces a character class, terminated by a
         closing square bracket. A closing square bracket on its own is not spe-
-        cial. If a closing square bracket is required as a member of the class,
+        cial by default.  However, if the PCRE_JAVASCRIPT_COMPAT option is set,
-        it should be the first data character in the class  (after  an  initial
+        a lone closing square bracket causes a compile-time error. If a closing
-        circumflex, if present) or escaped with a backslash.
+        square  bracket  is required as a member of the class, it should be the
+        first data character in the class  (after  an  initial  circumflex,  if
+        present) or escaped with a backslash.
         A  character  class matches a single character in the subject. In UTF-8
-        mode, the character may occupy more than one byte. A matched  character
+        mode, the character may be more than one byte long. A matched character
         must be in the set of characters defined by the class, unless the first
         character in the class definition is a circumflex, in  which  case  the
         subject  character  must  not  be in the set defined by the class. If a
-Line 3694 
 SQUARE BRACKETS AND CHARACTER CLASSES
+Line 3897 
 SQUARE BRACKETS AND CHARACTER CLASSES
         while [^aeiou] matches any character that is not a  lower  case  vowel.
         Note that a circumflex is just a convenient notation for specifying the
         characters that are in the class by enumerating those that are  not.  A
-        class  that starts with a circumflex is not an assertion: it still con-
+        class  that starts with a circumflex is not an assertion; it still con-
         sumes a character from the subject string, and therefore  it  fails  if
         the current pointer is at the end of the string.
-Line 3710 
 SQUARE BRACKETS AND CHARACTER CLASSES
+Line 3913 
 SQUARE BRACKETS AND CHARACTER CLASSES
         than 128, so caseless matching is always possible. For characters  with
         higher  values,  the  concept  of case is supported if PCRE is compiled
         with Unicode property support, but not otherwise.  If you want  to  use
-        caseless  matching  for  characters 128 and above, you must ensure that
+        caseless  matching  in UTF8-mode for characters 128 and above, you must
-        PCRE is compiled with Unicode property support as well  as  with  UTF-8
+        ensure that PCRE is compiled with Unicode property support as  well  as
-        support.
+        with UTF-8 support.
         Characters  that  might  indicate  line breaks are never treated in any
         special way  when  matching  character  classes,  whatever  line-ending
-Line 3749 
 SQUARE BRACKETS AND CHARACTER CLASSES
+Line 3952 
 SQUARE BRACKETS AND CHARACTER CLASSES
         concept  of  case for characters with values greater than 128 only when
         it is compiled with Unicode property support.
-        The character types \d, \D, \p, \P, \s, \S, \w, and \W may also  appear
+        The character types \d, \D, \h, \H, \p, \P, \s, \S, \v, \V, \w, and  \W
-        in  a  character  class,  and add the characters that they match to the
+        may  also appear in a character class, and add the characters that they
-        class. For example, [\dABCDEF] matches any hexadecimal digit. A circum-
+        match to the class. For example,  [\dABCDEF]  matches  any  hexadecimal
-        flex  can  conveniently  be used with the upper case character types to
+        digit.  A circumflex can conveniently be used with the upper case char-
-        specify a more restricted set of characters  than  the  matching  lower
+        acter types to specify a more restricted set  of  characters  than  the
-        case  type.  For example, the class [^\W_] matches any letter or digit,
+        matching  lower  case  type.  For example, the class [^\W_] matches any
-        but not underscore.
+        letter or digit, but not underscore.
         The only metacharacters that are recognized in  character  classes  are
         backslash,  hyphen  (only  where  it can be interpreted as specifying a
-Line 3774 
 POSIX CHARACTER CLASSES
+Line 3977 
 POSIX CHARACTER CLASSES
           [01[:alpha:]%]
         matches "0", "1", any alphabetic character, or "%". The supported class
-        names are
+        names are:
           alnum    letters and digits
           alpha    letters
-Line 3785 
 POSIX CHARACTER CLASSES
+Line 3988 
 POSIX CHARACTER CLASSES
           graph    printing characters, excluding space
           lower    lower case letters
           print    printing characters, including space
-          punct    printing characters, excluding letters and digits
+          punct    printing characters, excluding letters and digits and space
           space    white space (not quite the same as \s)
           upper    upper case letters
           word     "word" characters (same as \w)
-Line 3806 
 POSIX CHARACTER CLASSES
+Line 4009 
 POSIX CHARACTER CLASSES
         POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but
         these are not supported, and an error is given if they are encountered.
-        In UTF-8 mode, characters with values greater than 128 do not match any
+        By  default,  in UTF-8 mode, characters with values greater than 128 do
-        of the POSIX character classes.
+        not match any of the POSIX character classes. However, if the  PCRE_UCP
+        option  is passed to pcre_compile(), some of the classes are changed so
+        that Unicode character properties are used. This is achieved by replac-
+        ing the POSIX classes by other sequences, as follows:
+          [:alnum:]  becomes  \p{Xan}
+          [:alpha:]  becomes  \p{L}
+          [:blank:]  becomes  \h
+          [:digit:]  becomes  \p{Nd}
+          [:lower:]  becomes  \p{Ll}
+          [:space:]  becomes  \p{Xps}
+          [:upper:]  becomes  \p{Lu}
+          [:word:]   becomes  \p{Xwd}
+        Negated  versions,  such  as [:^alpha:] use \P instead of \p. The other
+        POSIX classes are unchanged, and match only characters with code points
+        less than 128.
  VERTICAL BAR
-        Vertical bar characters are used to separate alternative patterns.  For
+        Vertical  bar characters are used to separate alternative patterns. For
         example, the pattern
           gilbert|sullivan
-        matches  either "gilbert" or "sullivan". Any number of alternatives may
+        matches either "gilbert" or "sullivan". Any number of alternatives  may
-        appear, and an empty  alternative  is  permitted  (matching  the  empty
+        appear,  and  an  empty  alternative  is  permitted (matching the empty
         string). The matching process tries each alternative in turn, from left
-        to right, and the first one that succeeds is used. If the  alternatives
+        to  right, and the first one that succeeds is used. If the alternatives
-        are  within a subpattern (defined below), "succeeds" means matching the
+        are within a subpattern (defined below), "succeeds" means matching  the
         rest of the main pattern as well as the alternative in the subpattern.
  INTERNAL OPTION SETTING
-        The settings of the  PCRE_CASELESS,  PCRE_MULTILINE,  PCRE_DOTALL,  and
+        The  settings  of  the  PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and
-        PCRE_EXTENDED  options  (which are Perl-compatible) can be changed from
+        PCRE_EXTENDED options (which are Perl-compatible) can be  changed  from
-        within the pattern by  a  sequence  of  Perl  option  letters  enclosed
+        within  the  pattern  by  a  sequence  of  Perl option letters enclosed
         between "(?" and ")".  The option letters are
           i  for PCRE_CASELESS
-Line 3839 
 INTERNAL OPTION SETTING
+Line 4058 
 INTERNAL OPTION SETTING
         For example, (?im) sets caseless, multiline matching. It is also possi-
         ble to unset these options by preceding the letter with a hyphen, and a
-        combined  setting and unsetting such as (?im-sx), which sets PCRE_CASE-
+        combined setting and unsetting such as (?im-sx), which sets  PCRE_CASE-
-        LESS and PCRE_MULTILINE while unsetting PCRE_DOTALL and  PCRE_EXTENDED,
+        LESS  and PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED,
-        is  also  permitted.  If  a  letter  appears  both before and after the
+        is also permitted. If a  letter  appears  both  before  and  after  the
         hyphen, the option is unset.
-        The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and  PCRE_EXTRA
+        The  PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA
-        can  be changed in the same way as the Perl-compatible options by using
+        can be changed in the same way as the Perl-compatible options by  using
         the characters J, U and X respectively.
-        When one of these option changes occurs at  top  level  (that  is,  not
+        When  one  of  these  option  changes occurs at top level (that is, not
-        inside  subpattern parentheses), the change applies to the remainder of
+        inside subpattern parentheses), the change applies to the remainder  of
         the pattern that follows. If the change is placed right at the start of
         a pattern, PCRE extracts it into the global options (and it will there-
         fore show up in data extracted by the pcre_fullinfo() function).
-        An option change within a subpattern (see below for  a  description  of
+        An  option  change  within a subpattern (see below for a description of
         subpatterns) affects only that part of the current pattern that follows
         it, so
           (a(?i)b)c
         matches abc and aBc and no other strings (assuming PCRE_CASELESS is not
-        used).   By  this means, options can be made to have different settings
+        used).  By this means, options can be made to have  different  settings
-        in different parts of the pattern. Any changes made in one  alternative
+        in  different parts of the pattern. Any changes made in one alternative
-        do  carry  on  into subsequent branches within the same subpattern. For
+        do carry on into subsequent branches within the  same  subpattern.  For
         example,
           (a(?i)b|c)
-        matches "ab", "aB", "c", and "C", even though  when  matching  "C"  the
+        matches  "ab",  "aB",  "c",  and "C", even though when matching "C" the
-        first  branch  is  abandoned before the option setting. This is because
+        first branch is abandoned before the option setting.  This  is  because
-        the effects of option settings happen at compile time. There  would  be
+        the  effects  of option settings happen at compile time. There would be
         some very weird behaviour otherwise.
-        Note:  There  are  other  PCRE-specific  options that can be set by the
+        Note: There are other PCRE-specific options that  can  be  set  by  the
-        application when the compile or match functions  are  called.  In  some
+        application  when  the  compile  or match functions are called. In some
         cases the pattern can contain special leading sequences such as (*CRLF)
-        to override what the application has set or what  has  been  defaulted.
+        to  override  what  the application has set or what has been defaulted.
-        Details  are  given  in the section entitled "Newline sequences" above.
+        Details are given in the section entitled  "Newline  sequences"  above.
-        There is also the (*UTF8) leading sequence that  can  be  used  to  set
+        There  are  also  the  (*UTF8) and (*UCP) leading sequences that can be
-        UTF-8 mode; this is equivalent to setting the PCRE_UTF8 option.
+        used to set UTF-8 and Unicode property modes; they  are  equivalent  to
+        setting the PCRE_UTF8 and the PCRE_UCP options, respectively.
  SUBPATTERNS
-Line 3961 
 DUPLICATE SUBPATTERN NUMBERS
+Line 4181 
 DUPLICATE SUBPATTERN NUMBERS
           / ( a )  (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x
           # 1            2         2  3        2     3     4
-        A backreference or a recursive call to  a  numbered  subpattern  always
+        A back reference to a numbered subpattern uses the  most  recent  value
-        refers to the first one in the pattern with the given number.
+        that  is  set  for that number by any subpattern. The following pattern
+        matches "abcabc" or "defdef":
+          /(?|(abc)|(def))\1/
+        In contrast, a recursive or "subroutine" call to a numbered  subpattern
+        always  refers  to  the first one in the pattern with the given number.
+        The following pattern matches "abcabc" or "defabc":
+          /(?|(abc)|(def))(?1)/
+        If a condition test for a subpattern's having matched refers to a  non-
+        unique  number, the test is true if any of the subpatterns of that num-
+        ber have matched.
-        An  alternative approach to using this "branch reset" feature is to use
+        An alternative approach to using this "branch reset" feature is to  use
         duplicate named subpatterns, as described in the next section.
  NAMED SUBPATTERNS
-        Identifying capturing parentheses by number is simple, but  it  can  be
+        Identifying  capturing  parentheses  by number is simple, but it can be
-        very  hard  to keep track of the numbers in complicated regular expres-
+        very hard to keep track of the numbers in complicated  regular  expres-
-        sions. Furthermore, if an  expression  is  modified,  the  numbers  may
+        sions.  Furthermore,  if  an  expression  is  modified, the numbers may
-        change.  To help with this difficulty, PCRE supports the naming of sub-
+        change. To help with this difficulty, PCRE supports the naming of  sub-
         patterns. This feature was not added to Perl until release 5.10. Python
-        had  the  feature earlier, and PCRE introduced it at release 4.0, using
+        had the feature earlier, and PCRE introduced it at release  4.0,  using
-        the Python syntax. PCRE now supports both the Perl and the Python  syn-
+        the  Python syntax. PCRE now supports both the Perl and the Python syn-
-        tax.
+        tax. Perl allows identically numbered  subpatterns  to  have  different
+        names, but PCRE does not.
         In  PCRE,  a subpattern can be named in one of three ways: (?<name>...)
         or (?'name'...) as in Perl, or (?P<name>...) as in  Python.  References
-        to capturing parentheses from other parts of the pattern, such as back-
+        to  capturing parentheses from other parts of the pattern, such as back
         references, recursion, and conditions, can be made by name as  well  as
         by number.
-Line 3994 
 NAMED SUBPATTERNS
+Line 4228 
 NAMED SUBPATTERNS
         By default, a name must be unique within a pattern, but it is  possible
         to relax this constraint by setting the PCRE_DUPNAMES option at compile
-        time. This can be useful for patterns where only one  instance  of  the
+        time. (Duplicate names are also always permitted for  subpatterns  with
+        the  same  number, set up as described in the previous section.) Dupli-
+        cate names can be useful for patterns where only one  instance  of  the
         named  parentheses  can  match. Suppose you want to match the name of a
         weekday, either as a 3-letter abbreviation or as the full name, and  in
         both cases you want to extract the abbreviation. This pattern (ignoring
-Line 4013 
 NAMED SUBPATTERNS
+Line 4249 
 NAMED SUBPATTERNS
         The convenience function for extracting the data by  name  returns  the
         substring  for  the first (and in this example, the only) subpattern of
         that name that matched. This saves searching  to  find  which  numbered
-        subpattern  it  was. If you make a reference to a non-unique named sub-
+        subpattern it was.
-        pattern from elsewhere in the pattern, the one that corresponds to  the
-        lowest  number  is used. For further details of the interfaces for han-
+        If  you  make  a  back  reference to a non-unique named subpattern from
-        dling named subpatterns, see the pcreapi documentation.
+        elsewhere in the pattern, the one that corresponds to the first  occur-
+        rence of the name is used. In the absence of duplicate numbers (see the
+        previous section) this is the one with the lowest number. If you use  a
+        named  reference  in a condition test (see the section about conditions
+        below), either to check whether a subpattern has matched, or  to  check
+        for  recursion,  all  subpatterns with the same name are tested. If the
+        condition is true for any one of them, the overall condition  is  true.
+        This is the same behaviour as testing by number. For further details of
+        the interfaces for handling named subpatterns, see the pcreapi documen-
+        tation.
         Warning: You cannot use different names to distinguish between two sub-
-        patterns  with  the same number (see the previous section) because PCRE
+        patterns with the same number because PCRE uses only the  numbers  when
-        uses only the numbers when matching.
+        matching. For this reason, an error is given at compile time if differ-
+        ent names are given to subpatterns with the same number.  However,  you
+        can  give  the same name to subpatterns with the same number, even when
+        PCRE_DUPNAMES is not set.
  REPETITION
-Line 4037 
 REPETITION
+Line 4285 
 REPETITION
           a character class
           a back reference (see next section)
           a parenthesized subpattern (unless it is an assertion)
+          a recursive or "subroutine" call to a subpattern
         The  general repetition quantifier specifies a minimum and maximum num-
         ber of permitted matches, by giving the two numbers in  curly  brackets
-Line 4151 
 REPETITION
+Line 4400 
 REPETITION
         mization, or alternatively using ^ to indicate anchoring explicitly.
         However,  there is one situation where the optimization cannot be used.
-        When .*  is inside capturing parentheses that  are  the  subject  of  a
+        When .*  is inside capturing parentheses that are the subject of a back
-        backreference  elsewhere  in the pattern, a match at the start may fail
+        reference elsewhere in the pattern, a match at the start may fail where
-        where a later one succeeds. Consider, for example:
+        a later one succeeds. Consider, for example:
           (.*)abc\1
-Line 4360 
 BACK REFERENCES
+Line 4609 
 BACK REFERENCES
         There may be more than one back reference to the same subpattern. If  a
         subpattern  has  not actually been used in a particular match, any back
-        references to it always fail. For example, the pattern
+        references to it always fail by default. For example, the pattern
           (a|(bc))\2
-        always fails if it starts to match "a" rather than "bc". Because  there
+        always fails if it starts to match "a" rather than  "bc".  However,  if
-        may  be  many  capturing parentheses in a pattern, all digits following
+        the PCRE_JAVASCRIPT_COMPAT option is set at compile time, a back refer-
-        the backslash are taken as part of a potential back  reference  number.
+        ence to an unset value matches an empty string.
-        If the pattern continues with a digit character, some delimiter must be
-        used to terminate the back reference. If the  PCRE_EXTENDED  option  is
+        Because there may be many capturing parentheses in a pattern, all  dig-
-        set,  this  can  be  whitespace.  Otherwise an empty comment (see "Com-
+        its  following a backslash are taken as part of a potential back refer-
-        ments" below) can be used.
+        ence number.  If the pattern continues with  a  digit  character,  some
+        delimiter  must  be  used  to  terminate  the  back  reference.  If the
-        A back reference that occurs inside the parentheses to which it  refers
+        PCRE_EXTENDED option is set, this can be whitespace. Otherwise, the \g{
-        fails  when  the subpattern is first used, so, for example, (a\1) never
+        syntax or an empty comment (see "Comments" below) can be used.
-        matches.  However, such references can be useful inside  repeated  sub-
+    Recursive back references
+        A  back reference that occurs inside the parentheses to which it refers
+        fails when the subpattern is first used, so, for example,  (a\1)  never
+        matches.   However,  such references can be useful inside repeated sub-
         patterns. For example, the pattern
           (a|b\1)+
         matches any number of "a"s and also "aba", "ababbaa" etc. At each iter-
-        ation of the subpattern,  the  back  reference  matches  the  character
+        ation  of  the  subpattern,  the  back  reference matches the character
-        string  corresponding  to  the previous iteration. In order for this to
+        string corresponding to the previous iteration. In order  for  this  to
-        work, the pattern must be such that the first iteration does  not  need
+        work,  the  pattern must be such that the first iteration does not need
-        to  match the back reference. This can be done using alternation, as in
+        to match the back reference. This can be done using alternation, as  in
         the example above, or by a quantifier with a minimum of zero.
+        Back  references of this type cause the group that they reference to be
+        treated as an atomic group.  Once the whole group has been  matched,  a
+        subsequent  matching  failure cannot cause backtracking into the middle
+        of the group.
  ASSERTIONS
-Line 4433 
 ASSERTIONS
+Line 4692 
 ASSERTIONS
         If you want to force a matching failure at some point in a pattern, the
         most convenient way to do it is  with  (?!)  because  an  empty  string
         always  matches, so an assertion that requires there not to be an empty
-        string must always fail.
+        string must always fail.   The  Perl  5.10  backtracking  control  verb
+        (*FAIL) or (*F) is essentially a synonym for (?!).
     Lookbehind assertions
-        Lookbehind assertions start with (?<= for positive assertions and  (?<!
+        Lookbehind  assertions start with (?<= for positive assertions and (?<!
         for negative assertions. For example,
           (?<!foo)bar
-        does  find  an  occurrence  of "bar" that is not preceded by "foo". The
+        does find an occurrence of "bar" that is not  preceded  by  "foo".  The
-        contents of a lookbehind assertion are restricted  such  that  all  the
+        contents  of  a  lookbehind  assertion are restricted such that all the
         strings it matches must have a fixed length. However, if there are sev-
-        eral top-level alternatives, they do not all  have  to  have  the  same
+        eral  top-level  alternatives,  they  do  not all have to have the same
         fixed length. Thus
           (?<=bullock|donkey)
-Line 4454 
 ASSERTIONS
+Line 4714 
 ASSERTIONS
           (?<!dogs?|cats?)
-        causes  an  error at compile time. Branches that match different length
+        causes an error at compile time. Branches that match  different  length
-        strings are permitted only at the top level of a lookbehind  assertion.
+        strings  are permitted only at the top level of a lookbehind assertion.
-        This  is  an  extension  compared  with  Perl (at least for 5.8), which
+        This is an extension compared with Perl (5.8 and 5.10), which  requires
-        requires all branches to match the same length of string. An  assertion
+        all branches to match the same length of string. An assertion such as
-        such as
           (?<=ab(c|de))
         is  not  permitted,  because  its single top-level branch can match two
-        different lengths, but it is acceptable if rewritten to  use  two  top-
+        different lengths, but it is acceptable to PCRE if rewritten to use two
-        level branches:
+        top-level branches:
           (?<=abc|abde)
         In some cases, the Perl 5.10 escape sequence \K (see above) can be used
-        instead of a lookbehind assertion; this is not restricted to  a  fixed-
+        instead of  a  lookbehind  assertion  to  get  round  the  fixed-length
-        length.
+        restriction.
         The  implementation  of lookbehind assertions is, for each alternative,
         to temporarily move the current position back by the fixed  length  and
-Line 4482 
 ASSERTIONS
+Line 4741 
 ASSERTIONS
         ble to calculate the length of the lookbehind. The \X and  \R  escapes,
         which can match different numbers of bytes, are also not permitted.
+        "Subroutine"  calls  (see below) such as (?2) or (?&X) are permitted in
+        lookbehinds, as long as the subpattern matches a  fixed-length  string.
+        Recursion, however, is not supported.
         Possessive  quantifiers  can  be  used  in  conjunction with lookbehind
-        assertions to specify efficient matching at  the  end  of  the  subject
+        assertions to specify efficient matching of fixed-length strings at the
-        string. Consider a simple pattern such as
+        end of subject strings. Consider a simple pattern such as
           abcd$
-Line 4547 
 CONDITIONAL SUBPATTERNS
+Line 4810 
 CONDITIONAL SUBPATTERNS
         It  is possible to cause the matching process to obey a subpattern con-
         ditionally or to choose between two alternative subpatterns,  depending
-        on  the result of an assertion, or whether a previous capturing subpat-
+        on  the result of an assertion, or whether a specific capturing subpat-
-        tern matched or not. The two possible forms of  conditional  subpattern
+        tern has already been matched. The two possible  forms  of  conditional
-        are
+        subpattern are:
           (?(condition)yes-pattern)
           (?(condition)yes-pattern|no-pattern)
-Line 4564 
 CONDITIONAL SUBPATTERNS
+Line 4827 
 CONDITIONAL SUBPATTERNS
     Checking for a used subpattern by number
         If the text between the parentheses consists of a sequence  of  digits,
-        the  condition  is  true if the capturing subpattern of that number has
+        the condition is true if a capturing subpattern of that number has pre-
-        previously matched. An alternative notation is to  precede  the  digits
+        viously matched. If there is more than one  capturing  subpattern  with
-        with a plus or minus sign. In this case, the subpattern number is rela-
+        the  same  number  (see  the earlier section about duplicate subpattern
-        tive rather than absolute.  The most recently opened parentheses can be
+        numbers), the condition is true if any of them have been set. An alter-
-        referenced  by  (?(-1),  the  next most recent by (?(-2), and so on. In
+        native  notation is to precede the digits with a plus or minus sign. In
-        looping constructs it can also make sense to refer to subsequent groups
+        this case, the subpattern number is relative rather than absolute.  The
-        with constructs such as (?(+2).
+        most  recently opened parentheses can be referenced by (?(-1), the next
+        most recent by (?(-2), and so on. In looping  constructs  it  can  also
+        make  sense  to  refer  to  subsequent  groups  with constructs such as
+        (?(+2).
-        Consider  the  following  pattern, which contains non-significant white
+        Consider the following pattern, which  contains  non-significant  white
         space to make it more readable (assume the PCRE_EXTENDED option) and to
         divide it into three parts for ease of discussion:
           ( \( )?    [^()]+    (?(1) \) )
-        The  first  part  matches  an optional opening parenthesis, and if that
+        The first part matches an optional opening  parenthesis,  and  if  that
         character is present, sets it as the first captured substring. The sec-
-        ond  part  matches one or more characters that are not parentheses. The
+        ond part matches one or more characters that are not  parentheses.  The
         third part is a conditional subpattern that tests whether the first set
         of parentheses matched or not. If they did, that is, if subject started
         with an opening parenthesis, the condition is true, and so the yes-pat-
-        tern  is  executed  and  a  closing parenthesis is required. Otherwise,
+        tern is executed and a  closing  parenthesis  is  required.  Otherwise,
-        since no-pattern is not present, the  subpattern  matches  nothing.  In
+        since  no-pattern  is  not  present, the subpattern matches nothing. In
-        other  words,  this  pattern  matches  a  sequence  of non-parentheses,
+        other words,  this  pattern  matches  a  sequence  of  non-parentheses,
         optionally enclosed in parentheses.
-        If you were embedding this pattern in a larger one,  you  could  use  a
+        If  you  were  embedding  this pattern in a larger one, you could use a
         relative reference:
           ...other stuff... ( \( )?    [^()]+    (?(-1) \) ) ...
-        This  makes  the  fragment independent of the parentheses in the larger
+        This makes the fragment independent of the parentheses  in  the  larger
         pattern.
     Checking for a used subpattern by name
-        Perl uses the syntax (?(<name>)...) or (?('name')...)  to  test  for  a
+        Perl  uses  the  syntax  (?(<name>)...) or (?('name')...) to test for a
-        used  subpattern  by  name.  For compatibility with earlier versions of
+        used subpattern by name. For compatibility  with  earlier  versions  of
-        PCRE, which had this facility before Perl, the syntax  (?(name)...)  is
+        PCRE,  which  had this facility before Perl, the syntax (?(name)...) is
-        also  recognized. However, there is a possible ambiguity with this syn-
+        also recognized. However, there is a possible ambiguity with this  syn-
-        tax, because subpattern names may  consist  entirely  of  digits.  PCRE
+        tax,  because  subpattern  names  may  consist entirely of digits. PCRE
-        looks  first for a named subpattern; if it cannot find one and the name
+        looks first for a named subpattern; if it cannot find one and the  name
-        consists entirely of digits, PCRE looks for a subpattern of  that  num-
+        consists  entirely  of digits, PCRE looks for a subpattern of that num-
-        ber,  which must be greater than zero. Using subpattern names that con-
+        ber, which must be greater than zero. Using subpattern names that  con-
         sist entirely of digits is not recommended.
         Rewriting the above example to use a named subpattern gives this:
           (?<OPEN> \( )?    [^()]+    (?(<OPEN>) \) )
+        If  the  name used in a condition of this kind is a duplicate, the test
+        is applied to all subpatterns of the same name, and is true if any  one
+        of them has matched.
     Checking for pattern recursion
         If the condition is the string (R), and there is no subpattern with the
-        name  R, the condition is true if a recursive call to the whole pattern
+        name R, the condition is true if a recursive call to the whole  pattern
         or any subpattern has been made. If digits or a name preceded by amper-
         sand follow the letter R, for example:
           (?(R3)...) or (?(R&name)...)
-        the  condition is true if the most recent recursion is into the subpat-
+        the condition is true if the most recent recursion is into a subpattern
-        tern whose number or name is given. This condition does not  check  the
+        whose number or name is given. This condition does not check the entire
-        entire recursion stack.
+        recursion stack. If the name used in a condition  of  this  kind  is  a
+        duplicate, the test is applied to all subpatterns of the same name, and
+        is true if any one of them is the most recent recursion.
-        At  "top  level", all these recursion test conditions are false. Recur-
+        At "top level", all these recursion test  conditions  are  false.   The
-        sive patterns are described below.
+        syntax for recursive patterns is described below.
     Defining subpatterns for use by reference only
-        If the condition is the string (DEFINE), and  there  is  no  subpattern
+        If  the  condition  is  the string (DEFINE), and there is no subpattern
-        with  the  name  DEFINE,  the  condition is always false. In this case,
+        with the name DEFINE, the condition is  always  false.  In  this  case,
-        there may be only one alternative  in  the  subpattern.  It  is  always
+        there  may  be  only  one  alternative  in the subpattern. It is always
-        skipped  if  control  reaches  this  point  in the pattern; the idea of
+        skipped if control reaches this point  in  the  pattern;  the  idea  of
-        DEFINE is that it can be used to define "subroutines" that can be  ref-
+        DEFINE  is that it can be used to define "subroutines" that can be ref-
-        erenced  from elsewhere. (The use of "subroutines" is described below.)
+        erenced from elsewhere. (The use of "subroutines" is described  below.)
-        For example, a pattern to match an IPv4 address could be  written  like
+        For  example,  a pattern to match an IPv4 address could be written like
         this (ignore whitespace and line breaks):
           (?(DEFINE) (?<byte> 2[0-4]\d | 25[0-5] | 1\d\d | [1-9]?\d) )
           \b (?&byte) (\.(?&byte)){3} \b
-        The  first part of the pattern is a DEFINE group inside which a another
+        The first part of the pattern is a DEFINE group inside which a  another
-        group named "byte" is defined. This matches an individual component  of
+        group  named "byte" is defined. This matches an individual component of
-        an  IPv4  address  (a number less than 256). When matching takes place,
+        an IPv4 address (a number less than 256). When  matching  takes  place,
-        this part of the pattern is skipped because DEFINE acts  like  a  false
+        this  part  of  the pattern is skipped because DEFINE acts like a false
-        condition.
+        condition. The rest of the pattern uses references to the  named  group
+        to  match the four dot-separated components of an IPv4 address, insist-
-        The rest of the pattern uses references to the named group to match the
+        ing on a word boundary at each end.
-        four dot-separated components of an IPv4 address, insisting on  a  word
-        boundary at each end.
     Assertion conditions
-        If  the  condition  is  not  in any of the above formats, it must be an
+        If the condition is not in any of the above  formats,  it  must  be  an
-        assertion.  This may be a positive or negative lookahead or  lookbehind
+        assertion.   This may be a positive or negative lookahead or lookbehind
-        assertion.  Consider  this  pattern,  again  containing non-significant
+        assertion. Consider  this  pattern,  again  containing  non-significant
         white space, and with the two alternatives on the second line:
           (?(?=[^a-z]*[a-z])
           \d{2}-[a-z]{3}-\d{2}  |  \d{2}-\d{2}-\d{2} )
-        The condition  is  a  positive  lookahead  assertion  that  matches  an
+        The  condition  is  a  positive  lookahead  assertion  that  matches an
-        optional  sequence of non-letters followed by a letter. In other words,
+        optional sequence of non-letters followed by a letter. In other  words,
-        it tests for the presence of at least one letter in the subject.  If  a
+        it  tests  for the presence of at least one letter in the subject. If a
-        letter  is found, the subject is matched against the first alternative;
+        letter is found, the subject is matched against the first  alternative;
-        otherwise it is  matched  against  the  second.  This  pattern  matches
+        otherwise  it  is  matched  against  the  second.  This pattern matches
-        strings  in  one  of the two forms dd-aaa-dd or dd-dd-dd, where aaa are
+        strings in one of the two forms dd-aaa-dd or dd-dd-dd,  where  aaa  are
         letters and dd are digits.
  COMMENTS
-        The sequence (?# marks the start of a comment that continues up to  the
+        The  sequence (?# marks the start of a comment that continues up to the
-        next  closing  parenthesis.  Nested  parentheses are not permitted. The
+        next closing parenthesis. Nested parentheses  are  not  permitted.  The
-        characters that make up a comment play no part in the pattern  matching
+        characters  that make up a comment play no part in the pattern matching
         at all.
-        If  the PCRE_EXTENDED option is set, an unescaped # character outside a
+        If the PCRE_EXTENDED option is set, an unescaped # character outside  a
-        character class introduces a  comment  that  continues  to  immediately
+        character  class  introduces  a  comment  that continues to immediately
         after the next newline in the pattern.
  RECURSIVE PATTERNS
-        Consider  the problem of matching a string in parentheses, allowing for
+        Consider the problem of matching a string in parentheses, allowing  for
-        unlimited nested parentheses. Without the use of  recursion,  the  best
+        unlimited  nested  parentheses.  Without the use of recursion, the best
-        that  can  be  done  is  to use a pattern that matches up to some fixed
+        that can be done is to use a pattern that  matches  up  to  some  fixed
-        depth of nesting. It is not possible to  handle  an  arbitrary  nesting
+        depth  of  nesting.  It  is not possible to handle an arbitrary nesting
         depth.
         For some time, Perl has provided a facility that allows regular expres-
-        sions to recurse (amongst other things). It does this by  interpolating
+        sions  to recurse (amongst other things). It does this by interpolating
-        Perl  code in the expression at run time, and the code can refer to the
+        Perl code in the expression at run time, and the code can refer to  the
         expression itself. A Perl pattern using code interpolation to solve the
         parentheses problem can be created like this:
-Line 4705 
 RECURSIVE PATTERNS
+Line 4974 
 RECURSIVE PATTERNS
         refers recursively to the pattern in which it appears.
         Obviously, PCRE cannot support the interpolation of Perl code. Instead,
-        it  supports  special  syntax  for recursion of the entire pattern, and
+        it supports special syntax for recursion of  the  entire  pattern,  and
-        also for individual subpattern recursion.  After  its  introduction  in
+        also  for  individual  subpattern  recursion. After its introduction in
-        PCRE  and  Python,  this  kind of recursion was introduced into Perl at
+        PCRE and Python, this kind of  recursion  was  subsequently  introduced
-        release 5.10.
+        into Perl at release 5.10.
-        A special item that consists of (? followed by a  number  greater  than
+        A  special  item  that consists of (? followed by a number greater than
         zero and a closing parenthesis is a recursive call of the subpattern of
-        the given number, provided that it occurs inside that  subpattern.  (If
+        the  given  number, provided that it occurs inside that subpattern. (If
-        not,  it  is  a  "subroutine" call, which is described in the next sec-
+        not, it is a "subroutine" call, which is described  in  the  next  sec-
-        tion.) The special item (?R) or (?0) is a recursive call of the  entire
+        tion.)  The special item (?R) or (?0) is a recursive call of the entire
         regular expression.
-        In  PCRE (like Python, but unlike Perl), a recursive subpattern call is
-        always treated as an atomic group. That is, once it has matched some of
-        the subject string, it is never re-entered, even if it contains untried
-        alternatives and there is a subsequent matching failure.
         This PCRE pattern solves the nested  parentheses  problem  (assume  the
         PCRE_EXTENDED option is set so that white space is ignored):
-          \( ( (?>[^()]+) | (?R) )* \)
+          \( ( [^()]++ | (?R) )* \)
         First  it matches an opening parenthesis. Then it matches any number of
         substrings which can either be a  sequence  of  non-parentheses,  or  a
         recursive  match  of the pattern itself (that is, a correctly parenthe-
-        sized substring).  Finally there is a closing parenthesis.
+        sized substring).  Finally there is a closing parenthesis. Note the use
+        of a possessive quantifier to avoid backtracking into sequences of non-
+        parentheses.
         If this were part of a larger pattern, you would not  want  to  recurse
         the entire pattern, so instead you could use this:
-          ( \( ( (?>[^()]+) | (?1) )* \) )
+          ( \( ( [^()]++ | (?1) )* \) )
         We  have  put the pattern into parentheses, and caused the recursion to
         refer to them instead of the whole pattern.
         In a larger pattern,  keeping  track  of  parenthesis  numbers  can  be
-        tricky.  This is made easier by the use of relative references. (A Perl
+        tricky.  This  is made easier by the use of relative references (a Perl
-.10 feature.)  Instead of (?1) in the  pattern  above  you  can  write
+.10 feature).  Instead of (?1) in the  pattern  above  you  can  write
         (?-2) to refer to the second most recently opened parentheses preceding
         the recursion. In other  words,  a  negative  number  counts  capturing
         parentheses leftwards from the point at which it is encountered.
-Line 4757 
 RECURSIVE PATTERNS
+Line 5023 
 RECURSIVE PATTERNS
         syntax for this is (?&name); PCRE's earlier syntax  (?P>name)  is  also
         supported. We could rewrite the above example as follows:
-          (?<pn> \( ( (?>[^()]+) | (?&pn) )* \) )
+          (?<pn> \( ( [^()]++ | (?&pn) )* \) )
         If  there  is more than one subpattern with the same name, the earliest
         one is used.
         This particular example pattern that we have been looking  at  contains
-        nested  unlimited repeats, and so the use of atomic grouping for match-
+        nested unlimited repeats, and so the use of a possessive quantifier for
-        ing strings of non-parentheses is important when applying  the  pattern
+        matching strings of non-parentheses is important when applying the pat-
-        to strings that do not match. For example, when this pattern is applied
+        tern  to  strings  that do not match. For example, when this pattern is
-        to
+        applied to
           (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa()
-        it yields "no match" quickly. However, if atomic grouping is not  used,
+        it yields "no match" quickly. However, if a  possessive  quantifier  is
-        the  match  runs  for a very long time indeed because there are so many
+        not  used, the match runs for a very long time indeed because there are
-        different ways the + and * repeats can carve up the  subject,  and  all
+        so many different ways the + and * repeats can carve  up  the  subject,
-        have to be tested before failure can be reported.
+        and all have to be tested before failure can be reported.
-        At the end of a match, the values set for any capturing subpatterns are
+        At  the  end  of a match, the values of capturing parentheses are those
-        those from the outermost level of the recursion at which the subpattern
+        from the outermost level. If you want to obtain intermediate values,  a
-        value  is  set.   If  you want to obtain intermediate values, a callout
+        callout  function can be used (see below and the pcrecallout documenta-
-        function can be used (see below and the pcrecallout documentation).  If
+        tion). If the pattern above is matched against
-        the pattern above is matched against
           (ab(cd)ef)
-        the  value  for  the  capturing  parentheses is "ef", which is the last
+        the value for the inner capturing parentheses  (numbered  2)  is  "ef",
-        value taken on at the top level. If additional parentheses  are  added,
+        which  is the last value taken on at the top level. If a capturing sub-
-        giving
+        pattern is not matched at the top level, its final value is unset, even
+        if it is (temporarily) set at a deeper level.
-          \( ( ( (?>[^()]+) | (?R) )* ) \)
-             ^                        ^
+        If  there are more than 15 capturing parentheses in a pattern, PCRE has
-             ^                        ^
+        to obtain extra memory to store data during a recursion, which it  does
+        by using pcre_malloc, freeing it via pcre_free afterwards. If no memory
-        the  string  they  capture is "ab(cd)ef", the contents of the top level
+        can be obtained, the match fails with the PCRE_ERROR_NOMEMORY error.
-        parentheses. If there are more than 15 capturing parentheses in a  pat-
-        tern, PCRE has to obtain extra memory to store data during a recursion,
-        which it does by using pcre_malloc, freeing  it  via  pcre_free  after-
-        wards.  If  no  memory  can  be  obtained,  the  match  fails  with the
-        PCRE_ERROR_NOMEMORY error.
         Do not confuse the (?R) item with the condition (R),  which  tests  for
         recursion.   Consider  this pattern, which matches text in angle brack-
-Line 4810 
 RECURSIVE PATTERNS
+Line 5070 
 RECURSIVE PATTERNS
         two  different  alternatives for the recursive and non-recursive cases.
         The (?R) item is the actual recursive call.
+    Recursion difference from Perl
+        In PCRE (like Python, but unlike Perl), a recursive subpattern call  is
+        always treated as an atomic group. That is, once it has matched some of
+        the subject string, it is never re-entered, even if it contains untried
+        alternatives  and  there  is a subsequent matching failure. This can be
+        illustrated by the following pattern, which purports to match a  palin-
+        dromic  string  that contains an odd number of characters (for example,
+        "a", "aba", "abcba", "abcdcba"):
+          ^(.|(.)(?1)\2)$
+        The idea is that it either matches a single character, or two identical
+        characters  surrounding  a sub-palindrome. In Perl, this pattern works;
+        in PCRE it does not if the pattern is  longer  than  three  characters.
+        Consider the subject string "abcba":
+        At  the  top level, the first character is matched, but as it is not at
+        the end of the string, the first alternative fails; the second alterna-
+        tive is taken and the recursion kicks in. The recursive call to subpat-
+        tern 1 successfully matches the next character ("b").  (Note  that  the
+        beginning and end of line tests are not part of the recursion).
+        Back  at  the top level, the next character ("c") is compared with what
+        subpattern 2 matched, which was "a". This fails. Because the  recursion
+        is  treated  as  an atomic group, there are now no backtracking points,
+        and so the entire match fails. (Perl is able, at  this  point,  to  re-
+        enter  the  recursion  and try the second alternative.) However, if the
+        pattern is written with the alternatives in the other order, things are
+        different:
+          ^((.)(?1)\2|.)$
+        This  time,  the recursing alternative is tried first, and continues to
+        recurse until it runs out of characters, at which point  the  recursion
+        fails.  But  this  time  we  do  have another alternative to try at the
+        higher level. That is the big difference:  in  the  previous  case  the
+        remaining alternative is at a deeper recursion level, which PCRE cannot
+        use.
+        To change the pattern so that matches all palindromic strings, not just
+        those  with  an  odd number of characters, it is tempting to change the
+        pattern to this:
+          ^((.)(?1)\2|.?)$
+        Again, this works in Perl, but not in PCRE, and for  the  same  reason.
+        When  a  deeper  recursion has matched a single character, it cannot be
+        entered again in order to match an empty string.  The  solution  is  to
+        separate  the two cases, and write out the odd and even cases as alter-
+        natives at the higher level:
+          ^(?:((.)(?1)\2|)|((.)(?3)\4|.))
+        If you want to match typical palindromic phrases, the  pattern  has  to
+        ignore all non-word characters, which can be done like this:
+          ^\W*+(?:((.)\W*+(?1)\W*+\2|)|((.)\W*+(?3)\W*+\4|\W*+.\W*+))\W*+$
+        If run with the PCRE_CASELESS option, this pattern matches phrases such
+        as "A man, a plan, a canal: Panama!" and it works well in both PCRE and
+        Perl.  Note the use of the possessive quantifier *+ to avoid backtrack-
+        ing into sequences of non-word characters. Without this, PCRE  takes  a
+        great  deal  longer  (ten  times or more) to match typical phrases, and
+        Perl takes so long that you think it has gone into a loop.
+        WARNING: The palindrome-matching patterns above work only if  the  sub-
+        ject  string  does not start with a palindrome that is shorter than the
+        entire string.  For example, although "abcba" is correctly matched,  if
+        the  subject  is "ababa", PCRE finds the palindrome "aba" at the start,
+        then fails at top level because the end of the string does not  follow.
+        Once  again, it cannot jump back into the recursion to try other alter-
+        natives, so the entire match fails.
  SUBPATTERNS AS SUBROUTINES
-Line 4836 
 SUBPATTERNS AS SUBROUTINES
+Line 5170 
 SUBPATTERNS AS SUBROUTINES
         two strings. Another example is  given  in  the  discussion  of  DEFINE
         above.
-        Like recursive subpatterns, a "subroutine" call is always treated as an
+        Like  recursive  subpatterns, a subroutine call is always treated as an
         atomic group. That is, once it has matched some of the subject  string,
         it  is  never  re-entered, even if it contains untried alternatives and
-        there is a subsequent matching failure.
+        there is a subsequent matching failure. Any capturing parentheses  that
+        are  set  during  the  subroutine  call revert to their previous values
+        afterwards.
         When a subpattern is used as a subroutine, processing options  such  as
         case-independence are fixed when the subpattern is defined. They cannot
-Line 4922 
 BACKTRACKING CONTROL
+Line 5258 
 BACKTRACKING CONTROL
         (*FAIL), which behaves like a failing negative assertion, they cause an
         error if encountered by pcre_dfa_exec().
+        If any of these verbs are used in an assertion or subroutine subpattern
+        (including recursive subpatterns), their effect  is  confined  to  that
+        subpattern;  it  does  not extend to the surrounding pattern. Note that
+        such subpatterns are processed as anchored at the point where they  are
+        tested.
         The  new verbs make use of what was previously invalid syntax: an open-
-        ing parenthesis followed by an asterisk. In Perl, they are generally of
+        ing parenthesis followed by an asterisk. They are generally of the form
-        the form (*VERB:ARG) but PCRE does not support the use of arguments, so
+        (*VERB)  or (*VERB:NAME). Some may take either form, with differing be-
-        its general form is just (*VERB). Any number of these verbs  may  occur
+        haviour, depending on whether or not an argument is present. An name is
-        in a pattern. There are two kinds:
+        a  sequence  of letters, digits, and underscores. If the name is empty,
+        that is, if the closing parenthesis immediately follows the colon,  the
+        effect is as if the colon were not there. Any number of these verbs may
+        occur in a pattern.
+        PCRE contains some optimizations that are used to speed up matching  by
+        running some checks at the start of each match attempt. For example, it
+        may know the minimum length of matching subject, or that  a  particular
+        character  must  be present. When one of these optimizations suppresses
+        the running of a match, any included backtracking verbs  will  not,  of
+        course, be processed. You can suppress the start-of-match optimizations
+        by setting the PCRE_NO_START_OPTIMIZE option when calling pcre_exec().
     Verbs that act immediately
-        The following verbs act as soon as they are encountered:
+        The following verbs act as soon as they are encountered. They  may  not
+        be followed by a name.
            (*ACCEPT)
         This  verb causes the match to end successfully, skipping the remainder
         of the pattern. When inside a recursion, only the innermost pattern  is
-        ended  immediately.  PCRE  differs  from  Perl  in  what happens if the
+        ended  immediately.  If  (*ACCEPT) is inside capturing parentheses, the
-        (*ACCEPT) is inside capturing parentheses. In Perl, the data so far  is
+        data so far is captured. (This feature was added  to  PCRE  at  release
-        captured: in PCRE no data is captured. For example:
+.00.) For example:
-          A(A|B(*ACCEPT)|C)D
+          A((?:A|B(*ACCEPT)|C)D)
-        This  matches  "AB", "AAD", or "ACD", but when it matches "AB", no data
+        This  matches  "AB", "AAD", or "ACD"; when it matches "AB", "B" is cap-
-        is captured.
+        tured by the outer parentheses.
           (*FAIL) or (*F)
-Line 4959 
 BACKTRACKING CONTROL
+Line 5313 
 BACKTRACKING CONTROL
         A  match  with the string "aaaa" always fails, but the callout is taken
         before each backtrack happens (in this example, 10 times).
+    Recording which path was taken
+        There is one verb whose main purpose  is  to  track  how  a  match  was
+        arrived  at,  though  it  also  has a secondary use in conjunction with
+        advancing the match starting point (see (*SKIP) below).
+          (*MARK:NAME) or (*:NAME)
+        A name is always  required  with  this  verb.  There  may  be  as  many
+        instances  of  (*MARK) as you like in a pattern, and their names do not
+        have to be unique.
+        When a match succeeds, the name  of  the  last-encountered  (*MARK)  is
+        passed  back  to  the  caller  via  the  pcre_extra  data structure, as
+        described in the section on pcre_extra in the pcreapi documentation. No
+        data  is  returned  for a partial match. Here is an example of pcretest
+        output, where the /K modifier requests the retrieval and outputting  of
+        (*MARK) data:
+          /X(*MARK:A)Y|X(*MARK:B)Z/K
+          XY
+: XY
+          MK: A
+          XZ
+: XZ
+          MK: B
+        The (*MARK) name is tagged with "MK:" in this output, and in this exam-
+        ple it indicates which of the two alternatives matched. This is a  more
+        efficient  way of obtaining this information than putting each alterna-
+        tive in its own capturing parentheses.
+        A name may also be returned after a failed  match  if  the  final  path
+        through  the  pattern involves (*MARK). However, unless (*MARK) used in
+        conjunction with (*COMMIT), this is unlikely to  happen  for  an  unan-
+        chored pattern because, as the starting point for matching is advanced,
+        the final check is often with an empty string, causing a failure before
+        (*MARK) is reached. For example:
+          /X(*MARK:A)Y|X(*MARK:B)Z/K
+          XP
+          No match
+        There are three potential starting points for this match (starting with
+        X, starting with P, and with  an  empty  string).  If  the  pattern  is
+        anchored, the result is different:
+          /^X(*MARK:A)Y|^X(*MARK:B)Z/K
+          XP
+          No match, mark = B
+        PCRE's  start-of-match  optimizations can also interfere with this. For
+        example, if, as a result of a call to pcre_study(), it knows the  mini-
+        mum  subject  length for a match, a shorter subject will not be scanned
+        at all.
+        Note that similar anomalies (though different in detail) exist in Perl,
+        no  doubt  for the same reasons. The use of (*MARK) data after a failed
+        match of an unanchored pattern is not recommended, unless (*COMMIT)  is
+        involved.
     Verbs that act after backtracking
         The following verbs do nothing when they are encountered. Matching con-
-        tinues  with what follows, but if there is no subsequent match, a fail-
+        tinues with what follows, but if there is no subsequent match,  causing
-        ure is forced.  The verbs  differ  in  exactly  what  kind  of  failure
+        a  backtrack  to  the  verb, a failure is forced. That is, backtracking
-        occurs.
+        cannot pass to the left of the verb. However, when one of  these  verbs
+        appears  inside  an atomic group, its effect is confined to that group,
+        because once the group has been matched, there is never any  backtrack-
+        ing  into  it.  In  this situation, backtracking can "jump back" to the
+        left of the entire atomic group. (Remember also, as stated above,  that
+        this localization also applies in subroutine calls and assertions.)
+        These  verbs  differ  in exactly what kind of failure occurs when back-
+        tracking reaches them.
           (*COMMIT)
-        This  verb  causes  the whole match to fail outright if the rest of the
+        This verb, which may not be followed by a name, causes the whole  match
-        pattern does not match. Even if the pattern is unanchored,  no  further
+        to fail outright if the rest of the pattern does not match. Even if the
-        attempts  to find a match by advancing the start point take place. Once
+        pattern is unanchored, no further attempts to find a match by advancing
-        (*COMMIT) has been passed, pcre_exec() is committed to finding a  match
+        the  starting  point  take  place.  Once  (*COMMIT)  has  been  passed,
-        at the current starting point, or not at all. For example:
+        pcre_exec() is committed to finding a match  at  the  current  starting
+        point, or not at all. For example:
           a+(*COMMIT)b
         This  matches  "xxaab" but not "aacaab". It can be thought of as a kind
-        of dynamic anchor, or "I've started, so I must finish."
+        of dynamic anchor, or "I've started, so I must finish." The name of the
+        most  recently passed (*MARK) in the path is passed back when (*COMMIT)
-          (*PRUNE)
+        forces a match failure.
+        Note that (*COMMIT) at the start of a pattern is not  the  same  as  an
+        anchor,  unless  PCRE's start-of-match optimizations are turned off, as
+        shown in this pcretest example:
+          /(*COMMIT)abc/
+          xyzabc
+: abc
+          xyzabc\Y
+          No match
-        This verb causes the match to fail at the current position if the  rest
+        PCRE knows that any match must start  with  "a",  so  the  optimization
-        of the pattern does not match. If the pattern is unanchored, the normal
+        skips  along the subject to "a" before running the first match attempt,
-        "bumpalong" advance to the next starting character then happens.  Back-
+        which succeeds. When the optimization is disabled by the \Y  escape  in
-        tracking  can  occur as usual to the left of (*PRUNE), or when matching
+        the second subject, the match starts at "x" and so the (*COMMIT) causes
-        to the right of (*PRUNE), but if there is no match to the right,  back-
+        it to fail without trying any other starting points.
-        tracking  cannot  cross (*PRUNE).  In simple cases, the use of (*PRUNE)
-        is just an alternative to an atomic group or possessive quantifier, but
+          (*PRUNE) or (*PRUNE:NAME)
-        there  are  some uses of (*PRUNE) that cannot be expressed in any other
-        way.
+        This verb causes the match to fail at the current starting position  in
+        the  subject  if the rest of the pattern does not match. If the pattern
+        is unanchored, the normal "bumpalong"  advance  to  the  next  starting
+        character  then happens. Backtracking can occur as usual to the left of
+        (*PRUNE), before it is reached,  or  when  matching  to  the  right  of
+        (*PRUNE),  but  if  there is no match to the right, backtracking cannot