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

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-revision 172 by ph10,
Tue Jun  5 10:40:13 2007 UTC
+revision 469 by ph10,
Mon Oct 19 14:38:48 2009 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. There are
+ synopses of each function in the library have not been included. Neither has
- separate text files for the pcregrep and pcretest commands.
+ the pcredemo program. There are separate text files for the pcregrep and
+ pcretest commands.
  -----------------------------------------------------------------------------
-Line 18 
 INTRODUCTION
+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.)
+        tax,  there  is  some  support for one or two .NET and Oniguruma syntax
+        items, and there is an option for requesting some  minor  changes  that
-        The  current  implementation of PCRE (release 7.x) corresponds approxi-
+        give better JavaScript compatibility.
-        mately with Perl 5.10, including support for UTF-8 encoded strings  and
-        Unicode general category properties. However, UTF-8 and Unicode support
+        The  current implementation of PCRE corresponds approximately with Perl
-        has to be explicitly enabled; it is not the default. The Unicode tables
+.10, including support for UTF-8 encoded strings and  Unicode  general
-        correspond to Unicode release 5.0.0.
+        category  properties.  However,  UTF-8  and  Unicode  support has to be
+        explicitly enabled; it is not the default. The  Unicode  tables  corre-
+        spond to Unicode release 5.1.
         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 45 
 INTRODUCTION
+Line 48 
 INTRODUCTION
         Details of exactly which Perl regular expression features are  and  are
         not supported by PCRE are given in separate documents. See the pcrepat-
-        tern and pcrecompat pages.
+        tern and pcrecompat pages. There is a syntax summary in the  pcresyntax
+        page.
-        Some features of PCRE can be included, excluded, or  changed  when  the
+        Some  features  of  PCRE can be included, excluded, or changed when the
-        library  is  built.  The pcre_config() function makes it possible for a
+        library is built. The pcre_config() function makes it  possible  for  a
-        client to discover which features are  available.  The  features  them-
+        client  to  discover  which  features are available. The features them-
-        selves  are described in the pcrebuild page. Documentation about build-
+        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
+        The library contains a number of undocumented  internal  functions  and
-        data tables that are used by more than one  of  the  exported  external
+        data  tables  that  are  used by more than one of the exported external
-        functions,  but  which  are  not  intended for use by external callers.
+        functions, but which are not intended  for  use  by  external  callers.
-        Their names all begin with "_pcre_", which hopefully will  not  provoke
+        Their  names  all begin with "_pcre_", which hopefully will not provoke
         any name clashes. In some environments, it is possible to control which
-        external symbols are exported when a shared library is  built,  and  in
+        external  symbols  are  exported when a shared library is built, and in
         these cases the undocumented symbols are not exported.
  USER DOCUMENTATION
-        The  user  documentation  for PCRE comprises a number of different sec-
+        The user documentation for PCRE comprises a number  of  different  sec-
-        tions. In the "man" format, each of these is a separate "man page".  In
+        tions.  In the "man" format, each of these is a separate "man page". In
-        the  HTML  format, each is a separate page, linked from the index page.
+        the HTML format, each is a separate page, linked from the  index  page.
-        In the plain text format, all the sections are concatenated,  for  ease
+        In  the  plain  text format, all the sections, except the pcredemo sec-
-        of searching. The sections are as follows:
+        tion, are concatenated, for ease of searching. The sections are as fol-
+        lows:
           pcre              this document
           pcre-config       show PCRE installation configuration information
-Line 78 
 USER DOCUMENTATION
+Line 83 
 USER DOCUMENTATION
           pcrecallout       details of the callout feature
           pcrecompat        discussion of Perl compatibility
           pcrecpp           details of the C++ wrapper
+          pcredemo          a demonstration C program that uses PCRE
           pcregrep          description of the pcregrep command
           pcrematching      discussion of the two matching algorithms
           pcrepartial       details of the partial matching facility
-Line 86 
 USER DOCUMENTATION
+Line 92 
 USER DOCUMENTATION
           pcreperform       discussion of performance issues
           pcreposix         the POSIX-compatible C API
           pcreprecompile    details of saving and re-using precompiled patterns
-          pcresample        discussion of the sample program
+          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
+        In  addition,  in the "man" and HTML formats, there is a short page for
         each C library function, listing its arguments and results.
  LIMITATIONS
-        There  are some size limitations in PCRE but it is hoped that they will
+        There are some size limitations in PCRE but it is hoped that they  will
         never in practice be relevant.
-        The maximum length of a compiled pattern is 65539 (sic) bytes  if  PCRE
+        The  maximum  length of a compiled pattern is 65539 (sic) bytes if PCRE
         is compiled with the default internal linkage size of 2. If you want to
-        process regular expressions that are truly enormous,  you  can  compile
+        process  regular  expressions  that are truly enormous, you can compile
-        PCRE  with  an  internal linkage size of 3 or 4 (see the README file in
+        PCRE with an internal linkage size of 3 or 4 (see the  README  file  in
-        the source distribution and the pcrebuild documentation  for  details).
+        the  source  distribution and the pcrebuild documentation for details).
-        In  these  cases the limit is substantially larger.  However, the speed
+        In these cases the limit is substantially larger.  However,  the  speed
         of execution is slower.
-        All values in repeating quantifiers must be less than 65536. The  maxi-
+        All values in repeating quantifiers must be less than 65536.
-        mum  compiled  length  of  subpattern  with an explicit repeat count is
-bytes. The maximum number of capturing subpatterns is 65535.
         There is no limit to the number of parenthesized subpatterns, but there
         can be no more than 65535 capturing subpatterns.
-Line 117 
 LIMITATIONS
+Line 122 
 LIMITATIONS
         The maximum length of name for a named subpattern is 32 characters, and
         the maximum number of named subpatterns is 10000.
-        The maximum length of a subject string is the largest  positive  number
+        The  maximum  length of a subject string is the largest positive number
-        that  an integer variable can hold. However, when using the traditional
+        that an integer variable can hold. However, when using the  traditional
         matching function, PCRE uses recursion to handle subpatterns and indef-
-        inite  repetition.  This means that the available stack space may limit
+        inite repetition.  This means that the available stack space may  limit
         the size of a subject string that can be processed by certain patterns.
         For a discussion of stack issues, see the pcrestack documentation.
  UTF-8 AND UNICODE PROPERTY SUPPORT
-        From  release  3.3,  PCRE  has  had  some support for character strings
+        From release 3.3, PCRE has  had  some  support  for  character  strings
-        encoded in the UTF-8 format. For release 4.0 this was greatly  extended
+        encoded  in the UTF-8 format. For release 4.0 this was greatly extended
-        to  cover  most common requirements, and in release 5.0 additional sup-
+        to cover most common requirements, and in release 5.0  additional  sup-
         port for Unicode general category properties was added.
-        In order process UTF-8 strings, you must build PCRE  to  include  UTF-8
+        In  order  process  UTF-8 strings, you must build PCRE to include UTF-8
-        support  in  the  code,  and, in addition, you must call pcre_compile()
+        support in the code, and, in addition,  you  must  call  pcre_compile()
-        with the PCRE_UTF8 option flag. When you do this, both the pattern  and
+        with  the  PCRE_UTF8  option  flag,  or the pattern must start with the
-        any  subject  strings  that are matched against it are treated as UTF-8
+        sequence (*UTF8). When either of these is the case,  both  the  pattern
-        strings instead of just strings of bytes.
+        and  any  subject  strings  that  are matched against it are treated as
+        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 155 
 UTF-8 AND UNICODE PROPERTY SUPPORT
+Line 161 
 UTF-8 AND UNICODE PROPERTY SUPPORT
         optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE
         does not support this.
-        The following comments apply when PCRE is running in UTF-8 mode:
+    Validity of UTF-8 strings
+        When  you  set  the  PCRE_UTF8 flag, the strings passed as patterns and
+        subjects are (by default) checked for validity on entry to the relevant
+        functions.  From  release 7.3 of PCRE, the check is according the rules
+        of RFC 3629, which are themselves derived from the  Unicode  specifica-
+        tion.  Earlier  releases  of PCRE followed the rules of RFC 2279, which
+        allows the full range of 31-bit values (0 to 0x7FFFFFFF).  The  current
+        check allows only values in the range U+0 to U+10FFFF, excluding U+D800
+        to U+DFFF.
+        The excluded code points are the "Low Surrogate Area"  of  Unicode,  of
+        which  the Unicode Standard says this: "The Low Surrogate Area does not
+        contain any  character  assignments,  consequently  no  character  code
+        charts or namelists are provided for this area. Surrogates are reserved
+        for use with UTF-16 and then must be used in pairs."  The  code  points
+        that  are  encoded  by  UTF-16  pairs are available as independent code
+        points in the UTF-8 encoding. (In  other  words,  the  whole  surrogate
+        thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)
+        If  an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error return
+        (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know
+        that your strings are valid, and therefore want to skip these checks in
+        order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at
+        compile  time  or at run time, PCRE assumes that the pattern or subject
+        it is given (respectively) contains only valid  UTF-8  codes.  In  this
+        case, it does not diagnose an invalid UTF-8 string.
+        If  you  pass  an  invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set,
+        what happens depends on why the string is invalid. If the  string  con-
+        forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a
+        string of characters in the range 0  to  0x7FFFFFFF.  In  other  words,
+        apart from the initial validity test, PCRE (when in UTF-8 mode) handles
+        strings according to the more liberal rules of RFC  2279.  However,  if
+        the  string does not even conform to RFC 2279, the result is undefined.
+        Your program may crash.
+        If you want to process strings  of  values  in  the  full  range  0  to
+x7FFFFFFF,  encoded in a UTF-8-like manner as per the old RFC, you can
+        set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in
+        this situation, you will have to apply your own validity check.
-.  When you set the PCRE_UTF8 flag, the strings passed as patterns and
+    General comments about UTF-8 mode
-        subjects are checked for validity on entry to the  relevant  functions.
-        If an invalid UTF-8 string is passed, an error return is given. In some
-        situations, you may already know  that  your  strings  are  valid,  and
-        therefore want to skip these checks in order to improve performance. If
-        you set the PCRE_NO_UTF8_CHECK flag at compile time  or  at  run  time,
-        PCRE  assumes  that  the  pattern or subject it is given (respectively)
-        contains only valid UTF-8 codes. In this case, it does not diagnose  an
-        invalid  UTF-8 string. If you pass an invalid UTF-8 string to PCRE when
-        PCRE_NO_UTF8_CHECK is set, the results are undefined. Your program  may
-        crash.
 .  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a
         two-byte UTF-8 character if the value is greater than 127.
 . Octal numbers up to \777 are recognized, and  match  two-byte  UTF-8
         characters for values greater than \177.
 .  Repeat quantifiers apply to complete UTF-8 characters, not to indi-
         vidual bytes, for example: \x{100}{3}.
 . The dot metacharacter matches one UTF-8 character instead of a  sin-
         gle byte.
 .  The  escape sequence \C can be used to match a single byte in UTF-8
         mode, but its use can lead to some strange effects.  This  facility  is
         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-
         nizes  as  digits,  spaces,  or  word characters remain the same set as
         before, all with values less than 256. This remains true even when PCRE
         includes  Unicode  property support, because to do otherwise would slow
         down PCRE in many common cases. If you really want to test for a  wider
         sense  of,  say,  "digit",  you must use Unicode property tests such as
-        \p{Nd}.
+        \p{Nd}. Note that this also applies to \b, because  it  is  defined  in
+        terms of \w and \W.
-. Similarly, characters that match the POSIX named  character  classes
+.  Similarly,  characters that match the POSIX named character classes
         are all low-valued characters.
-.  Case-insensitive  matching  applies only to characters whose values
+. However, the Perl 5.10 horizontal and vertical  whitespace  matching
-        are less than 128, unless PCRE is built with Unicode property  support.
+        escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-
-        Even  when  Unicode  property support is available, PCRE still uses its
+        acters.
-        own character tables when checking the case of  low-valued  characters,
-        so  as not to degrade performance.  The Unicode property information is
+. Case-insensitive matching applies only to  characters  whose  values
+        are  less than 128, unless PCRE is built with Unicode property support.
+        Even when Unicode property support is available, PCRE  still  uses  its
+        own  character  tables when checking the case of low-valued characters,
+        so as not to degrade performance.  The Unicode property information  is
         used only for characters with higher values. Even when Unicode property
         support is available, PCRE supports case-insensitive matching only when
-        there is a one-to-one mapping between a letter's  cases.  There  are  a
+        there  is  a  one-to-one  mapping between a letter's cases. There are a
-        small  number  of  many-to-one  mappings in Unicode; these are not sup-
+        small number of many-to-one mappings in Unicode;  these  are  not  sup-
         ported by PCRE.
-Line 215 
 AUTHOR
+Line 256 
 AUTHOR
         University Computing Service
         Cambridge CB2 3QH, England.
-        Putting an actual email address here seems to have been a spam  magnet,
+        Putting  an actual email address here seems to have been a spam magnet,
-        so  I've  taken  it away. If you want to email me, use my two initials,
+        so I've taken it away. If you want to email me, use  my  two  initials,
         followed by the two digits 10, at the domain cam.ac.uk.
  REVISION
-        Last updated: 18 April 2007
+        Last updated: 28 September 2009
-        Copyright (c) 1997-2007 University of Cambridge.
+        Copyright (c) 1997-2009 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 237 
 NAME
+Line 278 
 NAME
  PCRE BUILD-TIME OPTIONS
         This  document  describes  the  optional  features  of PCRE that can be
-        selected when the library is compiled. They are all selected, or  dese-
+        selected when the library is compiled. It assumes use of the  configure
-        lected, by providing options to the configure script that is run before
+        script,  where the optional features are selected or deselected by pro-
-        the make command. The complete list of  options  for  configure  (which
+        viding options to configure before running the make  command.  However,
-        includes  the  standard  ones such as the selection of the installation
+        the  same  options  can be selected in both Unix-like and non-Unix-like
-        directory) can be obtained by running
+        environments using the GUI facility of cmake-gui if you are using CMake
+        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
+        obtained by running
           ./configure --help
-Line 266 
 C++ SUPPORT
+Line 317 
 C++ SUPPORT
  UTF-8 SUPPORT
-        To build PCRE with support for UTF-8 character strings, add
+        To build PCRE with support for UTF-8 Unicode character strings, add
           --enable-utf8
         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
         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
+        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
+        the  same  version  of  the  library.  Consequently,  --enable-utf8 and
+        --enable-ebcdic are mutually exclusive.
  UNICODE CHARACTER PROPERTY SUPPORT
-Line 296 
 UNICODE CHARACTER PROPERTY SUPPORT
+Line 353 
 UNICODE CHARACTER PROPERTY SUPPORT
  CODE VALUE OF NEWLINE
-        By  default,  PCRE interprets character 10 (linefeed, LF) 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
-        systems. You can compile PCRE to use character 13 (carriage return, CR)
+        systems.  You  can compile PCRE to use carriage return (CR) instead, by
-        instead, by adding
+        adding
           --enable-newline-is-cr
-Line 322 
 CODE VALUE OF NEWLINE
+Line 379 
 CODE VALUE OF NEWLINE
         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
+        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-
+        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 342 
 BUILDING SHARED AND STATIC LIBRARIES
+Line 412 
 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 357 
 POSIX MALLOC USAGE
+Line 427 
 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.  Separate  functions are provided because the usage is
+        ment functions. By default these point to malloc() and free(), but  you
-        very predictable: the block sizes requested are always  the  same,  and
+        can replace the pointers so that your own functions are used instead.
-        the  blocks  are always freed in reverse order. A calling program might
-        be able to implement optimized functions that perform better  than  the
+        Separate  functions  are  provided  rather  than  using pcre_malloc and
-        standard  malloc()  and  free()  functions.  PCRE  runs noticeably more
+        pcre_free because the  usage  is  very  predictable:  the  block  sizes
-        slowly when built in this way. This option affects only the pcre_exec()
+        requested  are  always  the  same,  and  the blocks are always freed in
-        function; it is not relevant for the the pcre_dfa_exec() function.
+        reverse order. A calling program might be able to  implement  optimized
+        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 pcre_dfa_exec().
  LIMITING PCRE RESOURCE USAGE
-Line 451 
 USING EBCDIC CODE
+Line 524 
 USING EBCDIC CODE
         PCRE  assumes  by  default that it will run in an environment where the
         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).
-        PCRE  can,  however,  be  compiled  to  run in an EBCDIC environment by
+        This  is  the  case for most computer operating systems. PCRE can, how-
-        adding
+        ever, be compiled to run in an EBCDIC environment by adding
           --enable-ebcdic
         to the configure command. This setting implies --enable-rebuild-charta-
-        bles.
+        bles.  You  should  only  use  it if you know that you are in an EBCDIC
+        environment (for example,  an  IBM  mainframe  operating  system).  The
+        --enable-ebcdic option is incompatible with --enable-utf8.
+ PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
+        By default, pcregrep reads all files as plain text. You can build it so
+        that it recognizes files whose names end in .gz or .bz2, and reads them
+        with libz or libbz2, respectively, by adding one or both of
+          --enable-pcregrep-libz
+          --enable-pcregrep-libbz2
+        to the configure command. These options naturally require that the rel-
+        evant libraries are installed on your system. Configuration  will  fail
+        if they are not.
+ PCRETEST OPTION FOR LIBREADLINE SUPPORT
+        If you add
+          --enable-pcretest-libreadline
+        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-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
+        pcretest build. In many operating environments with  a  sytem-installed
+        libreadline this is sufficient. However, in some environments (e.g.  if
+        an unmodified distribution version of readline is in use),  some  extra
+        configuration  may  be necessary. The INSTALL file for libreadline says
+        this:
+          "Readline uses the termcap functions, but does not link with the
+          termcap or curses library itself, allowing applications which link
+          with readline the to choose an appropriate library."
+        If your environment has not been set up so that an appropriate  library
+        is automatically included, you may need to add something like
+          LIBS="-ncurses"
+        immediately before the configure command.
  SEE ALSO
-Line 474 
 AUTHOR
+Line 594 
 AUTHOR
  REVISION
-        Last updated: 16 April 2007
+        Last updated: 29 September 2009
-        Copyright (c) 1997-2007 University of Cambridge.
+        Copyright (c) 1997-2009 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 562 
 THE ALTERNATIVE MATCHING ALGORITHM
+Line 682 
 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 618 
 THE ALTERNATIVE MATCHING ALGORITHM
+Line 744 
 THE ALTERNATIVE MATCHING ALGORITHM
 .  Callouts  are  supported, but the value of the capture_top field is
         always 1, and the value of the capture_last field is always -1.
-.  The \C escape sequence, which (in the standard algorithm) matches a
+. The \C escape sequence, which (in the standard algorithm) matches  a
         single  byte, even in UTF-8 mode, is not supported because the alterna-
         tive algorithm moves through the subject  string  one  character  at  a
         time, for all active paths through the tree.
+.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)
+        are not supported. (*FAIL) is supported, and  behaves  like  a  failing
+        negative assertion.
  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
-Line 634 
 ADVANTAGES OF THE ALTERNATIVE ALGORITHM
+Line 764 
 ADVANTAGES OF THE ALTERNATIVE ALGORITHM
         more than one match using the standard algorithm, you have to do kludgy
         things with callouts.
-.  There is much better support for partial matching. The restrictions
+.  Because  the  alternative  algorithm  scans the subject string just
-        on the content of the pattern that apply when using the standard  algo-
-        rithm  for  partial matching do not apply to the alternative algorithm.
-        For non-anchored patterns, the starting position of a partial match  is
-        available.
-.  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 669 
 AUTHOR
+Line 794 
 AUTHOR
  REVISION
-        Last updated: 29 May 2007
+        Last updated: 29 September 2009
-        Copyright (c) 1997-2007 University of Cambridge.
+        Copyright (c) 1997-2009 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 781 
 PCRE API OVERVIEW
+Line 906 
 PCRE API OVERVIEW
         pcre_exec() are used for compiling and matching regular expressions  in
         a  Perl-compatible  manner. A sample program that demonstrates the sim-
         plest way of using them is provided in the file  called  pcredemo.c  in
-        the  source distribution. The pcresample documentation describes how to
+        the PCRE source distribution. A listing of this program is given in the
-        run it.
+        pcredemo documentation, and the pcresample documentation describes  how
+        to compile and run it.
         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
-        ble,  is  also provided. This uses a different algorithm for the match-
+        ble, is also provided. This uses a different algorithm for  the  match-
-        ing. The alternative algorithm finds all possible matches (at  a  given
+        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
         convenience functions for extracting captured substrings from a subject
-Line 866 
 NEWLINES
+Line 993 
 NEWLINES
         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
+        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. The choice of newline convention  does
+        ment for a non-anchored pattern. There is more detail about this in the
-        not affect the interpretation of the \n or \r escape sequences.
+        section on pcre_exec() options below.
+        The choice of newline convention does not affect the interpretation  of
+        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.
-Line 926 
 CHECKING BUILD-TIME OPTIONS
+Line 1062 
 CHECKING BUILD-TIME OPTIONS
         The output is an integer whose value specifies  the  default  character
         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. The default should normally be the standard sequence
+        and  -1  for  ANY.  Though they are derived from ASCII, the same values
-        for your operating system.
+        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
+        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 an integer that gives the default limit for the number of
+        The output is a long integer that gives the default limit for the  num-
-        internal matching function calls in a  pcre_exec()  execution.  Further
+        ber  of  internal  matching  function calls in a pcre_exec() execution.
-        details are given with pcre_exec() below.
+        Further details are given with pcre_exec() below.
           PCRE_CONFIG_MATCH_LIMIT_RECURSION
-        The  output is an integer that gives the default limit for the depth of
+        The output is a long integer that gives the default limit for the depth
-        recursion when calling the internal matching function in a  pcre_exec()
+        of   recursion  when  calling  the  internal  matching  function  in  a
-        execution. Further details are given with pcre_exec() below.
+        pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
+        below.
           PCRE_CONFIG_STACKRECURSE
-Line 981 
 COMPILING A PATTERN
+Line 1127 
 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,
-        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
-Line 998 
 COMPILING A PATTERN
+Line 1146 
 COMPILING A PATTERN
         The options argument contains various bit settings that affect the com-
         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, can also be set and  unset  from  within  the
+        are compatible with Perl, but some others as well) can also be set  and
-        pattern  (see  the  detailed  description in the pcrepattern documenta-
+        unset  from  within  the  pattern  (see the detailed description in the
-        tion). For these options, the contents of the options  argument  speci-
+        pcrepattern documentation). For those options that can be different  in
-        fies  their initial settings at the start of compilation and execution.
+        different  parts  of  the pattern, the contents of the options argument
-        The PCRE_ANCHORED and PCRE_NEWLINE_xxx options can be set at  the  time
+        specifies their settings at the start of compilation and execution. The
-        of matching as well as at compile time.
+        PCRE_ANCHORED, PCRE_BSR_xxx, and PCRE_NEWLINE_xxx options can be set at
+        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 1041 
 COMPILING A PATTERN
+Line 1192 
 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,
+        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 a warning for this.)
-        There  are  at  present no other features controlled by this option. It
+        There are at present no other features controlled by  this  option.  It
         can also be set by a (?X) option setting within a pattern.
           PCRE_FIRSTLINE
-        If this option is set, an  unanchored  pattern  is  required  to  match
+        If  this  option  is  set,  an  unanchored pattern is required to match
-        before  or  at  the  first  newline  in  the subject string, though the
+        before or at the first  newline  in  the  subject  string,  though  the
         matched text may continue over the newline.
+          PCRE_JAVASCRIPT_COMPAT
+        If this option is set, PCRE's behaviour is changed in some ways so that
+        it is compatible with JavaScript rather than Perl. The changes  are  as
+        follows:
+        (1)  A  lone  closing square bracket in a pattern causes a compile-time
+        error, because this is illegal in JavaScript (by default it is  treated
+        as a data character). Thus, the pattern AB]CD becomes illegal when this
+        option is set.
+        (2) At run time, a back reference to an unset subpattern group  matches
+        an  empty  string (by default this causes the current matching alterna-
+        tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
+        set  (assuming  it can find an "a" in the subject), whereas it fails by
+        default, for Perl compatibility.
           PCRE_MULTILINE
         By default, PCRE treats the subject string as consisting  of  a  single
-Line 1184 
 COMPILING A PATTERN
+Line 1361 
 COMPILING A PATTERN
         and are therefore ignored.
         The newline option that is set at compile time becomes the default that
-        is  used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
+        is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
           PCRE_NO_AUTO_CAPTURE
         If this option is set, it disables the use of numbered capturing paren-
-        theses  in the pattern. Any opening parenthesis that is not followed by
+        theses in the pattern. Any opening parenthesis that is not followed  by
-        ? behaves as if it were followed by ?: but named parentheses can  still
+        ?  behaves as if it were followed by ?: but named parentheses can still
-        be  used  for  capturing  (and  they acquire numbers in the usual way).
+        be used for capturing (and they acquire  numbers  in  the  usual  way).
         There is no equivalent of this option in Perl.
           PCRE_UNGREEDY
-        This option inverts the "greediness" of the quantifiers  so  that  they
+        This  option  inverts  the "greediness" of the quantifiers so that they
-        are  not greedy by default, but become greedy if followed by "?". It is
+        are not greedy by default, but become greedy if followed by "?". It  is
-        not compatible with Perl. It can also be set by a (?U)  option  setting
+        not  compatible  with Perl. It can also be set by a (?U) option setting
         within the pattern.
           PCRE_UTF8
-        This  option  causes PCRE to regard both the pattern and the subject as
+        This option causes PCRE to regard both the pattern and the  subject  as
-        strings of UTF-8 characters instead of single-byte  character  strings.
+        strings  of  UTF-8 characters instead of single-byte character strings.
-        However,  it is available only when PCRE is built to include UTF-8 sup-
+        However, it is available only when PCRE is built to include UTF-8  sup-
-        port. If not, the use of this option provokes an error. Details of  how
+        port.  If not, the use of this option provokes an error. Details of how
-        this  option  changes the behaviour of PCRE are given in the section on
+        this option changes the behaviour of PCRE are given in the  section  on
         UTF-8 support in the main pcre page.
           PCRE_NO_UTF8_CHECK
         When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
-        automatically  checked. If an invalid UTF-8 sequence of bytes is found,
+        automatically checked. There is a  discussion  about  the  validity  of
-        pcre_compile() returns an error. If you already know that your  pattern
+        UTF-8  strings  in  the main pcre page. If an invalid UTF-8 sequence of
-        is  valid, and you want to skip this check for performance reasons, you
+        bytes is found, pcre_compile() returns an error. If  you  already  know
-        can set the PCRE_NO_UTF8_CHECK option. When it is set,  the  effect  of
+        that your pattern is valid, and you want to skip this check for perfor-
-        passing an invalid UTF-8 string as a pattern is undefined. It may cause
+        mance reasons, you can set the PCRE_NO_UTF8_CHECK option.  When  it  is
-        your program to crash.  Note that this option can  also  be  passed  to
+        set,  the  effect  of  passing  an invalid UTF-8 string as a pattern is
-        pcre_exec()  and pcre_dfa_exec(), to suppress the UTF-8 validity check-
+        undefined. It may cause your program to crash. Note  that  this  option
-        ing of subject strings.
+        can  also be passed to pcre_exec() and pcre_dfa_exec(), to suppress the
+        UTF-8 validity checking of subject strings.
  COMPILATION ERROR CODES
-Line 1242 
 COMPILATION ERROR CODES
+Line 1420 
 COMPILATION ERROR CODES
  nothing to repeat
  [this code is not in use]
  internal error: unexpected repeat
- unrecognized character after (?
+ unrecognized character after (? or (?-
  POSIX named classes are supported only within a class
  missing )
  reference to non-existent subpattern
-Line 1250 
 COMPILATION ERROR CODES
+Line 1428 
 COMPILATION ERROR CODES
  unknown option bit(s) set
  missing ) after comment
  [this code is not in use]
- regular expression too large
+ regular expression is too large
  failed to get memory
  unmatched parentheses
  internal error: code overflow
-Line 1259 
 COMPILATION ERROR CODES
+Line 1437 
 COMPILATION ERROR CODES
  malformed number or name after (?(
  conditional group contains more than two branches
  assertion expected after (?(
- (?R or (?digits must be followed by )
+ (?R or (?[+-]digits must be followed by )
  unknown POSIX class name
  POSIX collating elements are not supported
  this version of PCRE is not compiled with PCRE_UTF8 support
-Line 1279 
 COMPILATION ERROR CODES
+Line 1457 
 COMPILATION ERROR CODES
  malformed \P or \p sequence
  unknown property name after \P or \p
  subpattern name is too long (maximum 32 characters)
- too many named subpatterns (maximum 10,000)
+ too many named subpatterns (maximum 10000)
- repeated subpattern is too long
+ [this code is not in use]
  octal value is greater than \377 (not in UTF-8 mode)
  internal error: overran compiling workspace
   internal  error:  previously-checked  referenced  subpattern not
         found
  DEFINE group contains more than one branch
  repeating a DEFINE group is not allowed
- inconsistent NEWLINE options"
+ inconsistent NEWLINE options
+ \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
+ (*VERB) not recognized
+ number is too big
+ subpattern name expected
+ digit expected after (?+
+ ] is an invalid data character in JavaScript compatibility mode
+        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.
  STUDYING A PATTERN
-Line 1295 
 STUDYING A PATTERN
+Line 1485 
 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 1331 
 STUDYING A PATTERN
+Line 1521 
 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 1476 
 INFORMATION ABOUT A PATTERN
+Line 1675 
 INFORMATION ABOUT A PATTERN
         returned. The fourth argument should point to an unsigned char *  vari-
         able.
+          PCRE_INFO_HASCRORLF
+        Return  1  if  the  pattern  contains any explicit matches for CR or LF
+        characters, otherwise 0. The fourth argument should  point  to  an  int
+        variable.  An explicit match is either a literal CR or LF character, or
+        \r or \n.
           PCRE_INFO_JCHANGED
-        Return  1  if the (?J) option setting is used in the pattern, otherwise
+        Return 1 if the (?J) or (?-J) option setting is used  in  the  pattern,
-. The fourth argument should point to an int variable. The (?J) inter-
+        otherwise  0. The fourth argument should point to an int variable. (?J)
-        nal option setting changes the local PCRE_DUPNAMES value.
+        and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
           PCRE_INFO_LASTLITERAL
-        Return  the  value of the rightmost literal byte that must exist in any
+        Return the value of the rightmost literal byte that must exist  in  any
-        matched string, other than at its  start,  if  such  a  byte  has  been
+        matched  string,  other  than  at  its  start,  if such a byte has been
         recorded. The fourth argument should point to an int variable. If there
-        is no such byte, -1 is returned. For anchored patterns, a last  literal
+        is  no such byte, -1 is returned. For anchored patterns, a last literal
-        byte  is  recorded only if it follows something of variable length. For
+        byte is recorded only if it follows something of variable  length.  For
         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
-        PCRE  supports the use of named as well as numbered capturing parenthe-
+        PCRE supports the use of named as well as numbered capturing  parenthe-
-        ses. The names are just an additional way of identifying the  parenthe-
+        ses.  The names are just an additional way of identifying the parenthe-
         ses, which still acquire numbers. Several convenience functions such as
-        pcre_get_named_substring() are provided for  extracting  captured  sub-
+        pcre_get_named_substring()  are  provided  for extracting captured sub-
-        strings  by  name. It is also possible to extract the data directly, by
+        strings by name. It is also possible to extract the data  directly,  by
-        first converting the name to a number in order to  access  the  correct
+        first  converting  the  name to a number in order to access the correct
         pointers in the output vector (described with pcre_exec() below). To do
-        the conversion, you need  to  use  the  name-to-number  map,  which  is
+        the  conversion,  you  need  to  use  the  name-to-number map, which is
         described by these three values.
         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
-        of  each  entry;  both  of  these  return  an int value. The entry size
+        of each entry; both of these  return  an  int  value.  The  entry  size
-        depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns
+        depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns
-        a  pointer  to  the  first  entry of the table (a pointer to char). The
+        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-
+        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) )
-        There are four named subpatterns, so the table has  four  entries,  and
+        There  are  four  named subpatterns, so the table has four entries, and
-        each  entry  in the table is eight bytes long. The table is as follows,
+        each entry in the table is eight bytes long. The table is  as  follows,
         with non-printing bytes shows in hexadecimal, and undefined bytes shown
         as ??:
-Line 1532 
 INFORMATION ABOUT A PATTERN
+Line 1758 
 INFORMATION ABOUT A PATTERN
 04 m  o  n  t  h  00
 02 y  e  a  r  00 ??
-        When  writing  code  to  extract  data from named subpatterns using the
+        When writing code to extract data  from  named  subpatterns  using  the
-        name-to-number map, remember that the length of the entries  is  likely
+        name-to-number  map,  remember that the length of the entries is likely
         to be different for each compiled 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.  The  pcrepartial
+        pcre_exec(),  otherwise  0.  The fourth argument should point to an int
-        documentation  lists  the restrictions that apply to patterns when par-
+        variable. From  release  8.00,  this  always  returns  1,  because  the
-        tial matching is used.
+        restrictions  that  previously  applied  to  partial matching have been
+        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 within the pattern itself.
+        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
+        starts. For example, if the pattern /(?im)abc(?-i)d/ is  compiled  with
+        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 1564 
 INFORMATION ABOUT A PATTERN
+Line 1796 
 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 1572 
 INFORMATION ABOUT A PATTERN
+Line 1804 
 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 1628 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 1861 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
              const char *subject, int length, int startoffset,
              int options, int *ovector, int ovecsize);
-        The function pcre_exec() is called to match a subject string against  a
+        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
+        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,
+        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-
+        an alternative matching function, which is described below in the  sec-
         tion about the pcre_dfa_exec() function.
-        In most applications, the pattern will have been compiled (and  option-
+        In  most applications, the pattern will have been compiled (and option-
-        ally  studied)  in the same process that calls pcre_exec(). However, it
+        ally studied) in the same process that calls pcre_exec().  However,  it
         is possible to save compiled patterns and study data, and then use them
-        later  in  different processes, possibly even on different hosts. For a
+        later in different processes, possibly even on different hosts.  For  a
         discussion about this, see the pcreprecompile documentation.
         Here is an example of a simple call to pcre_exec():
-Line 1658 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 1891 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
     Extra data for pcre_exec()
-        If the extra argument is not NULL, it must point to a  pcre_extra  data
+        If  the  extra argument is not NULL, it must point to a pcre_extra data
-        block.  The pcre_study() function returns such a block (when it doesn't
+        block. The pcre_study() function returns such a block (when it  doesn't
-        return NULL), but you can also create one for yourself, and pass  addi-
+        return  NULL), but you can also create one for yourself, and pass addi-
-        tional  information  in it. The pcre_extra block contains the following
+        tional information in it. The pcre_extra block contains  the  following
         fields (not necessarily in this order):
           unsigned long int flags;
-Line 1671 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 1904 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
           void *callout_data;
           const unsigned char *tables;
-        The flags field is a bitmap that specifies which of  the  other  fields
+        The  flags  field  is a bitmap that specifies which of the other fields
         are set. The flag bits are:
           PCRE_EXTRA_STUDY_DATA
-Line 1680 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 1913 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
           PCRE_EXTRA_CALLOUT_DATA
           PCRE_EXTRA_TABLES
-        Other  flag  bits should be set to zero. The study_data field is set in
+        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
+        the  pcre_extra  block  that is returned by pcre_study(), together with
         the appropriate flag bit. You should not set this yourself, but you may
-        add to the block by setting the other fields  and  their  corresponding
+        add  to  the  block by setting the other fields and their corresponding
         flag bits.
         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
+        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
+        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-
+        Internally, PCRE uses a function called match() which it calls  repeat-
-        edly (sometimes recursively). The limit set by match_limit  is  imposed
+        edly  (sometimes  recursively). The limit set by match_limit is imposed
-        on  the  number  of times this function is called during a match, which
+        on the number of times this function is called during  a  match,  which
-        has the effect of limiting the amount of  backtracking  that  can  take
+        has  the  effect  of  limiting the amount of backtracking that can take
         place. For patterns that are not anchored, the count restarts from zero
         for each position in the subject string.
-        The default value for the limit can be set  when  PCRE  is  built;  the
+        The  default  value  for  the  limit can be set when PCRE is built; the
-        default  default  is 10 million, which handles all but the most extreme
+        default default is 10 million, which handles all but the  most  extreme
-        cases. You can override the default  by  suppling  pcre_exec()  with  a
+        cases.  You  can  override  the  default by suppling pcre_exec() with a
-        pcre_extra     block    in    which    match_limit    is    set,    and
+        pcre_extra    block    in    which    match_limit    is    set,     and
-        PCRE_EXTRA_MATCH_LIMIT is set in the  flags  field.  If  the  limit  is
+        PCRE_EXTRA_MATCH_LIMIT  is  set  in  the  flags  field. If the limit is
         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
-        The  match_limit_recursion field is similar to match_limit, but instead
+        The match_limit_recursion field is similar to match_limit, but  instead
         of limiting the total number of times that match() is called, it limits
-        the  depth  of  recursion. The recursion depth is a smaller number than
+        the depth of recursion. The recursion depth is a  smaller  number  than
-        the total number of calls, because not all calls to match() are  recur-
+        the  total number of calls, because not all calls to match() are recur-
         sive.  This limit is of use only if it is set smaller than match_limit.
         Limiting the recursion depth limits the amount of  stack  that  can  be
-Line 1723 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 1956 
 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 1741 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 1974 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
         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_UTF8_CHECK   and
+        PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,
-        PCRE_PARTIAL.
+        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,
+        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
           PCRE_NEWLINE_LF
           PCRE_NEWLINE_CRLF
-Line 1762 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 2004 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
         tion  of  pcre_compile()  above.  During  matching,  the newline choice
         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-
         ters.  It may also alter the way the match position is advanced after a
-        match  failure  for  an  unanchored  pattern.  When  PCRE_NEWLINE_CRLF,
+        match failure for an unanchored pattern.
-        PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY is set, and a match attempt
-        fails when the current position is at a CRLF sequence, the match  posi-
+        When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is
-        tion  is  advanced by two characters instead of one, in other words, to
+        set,  and a match attempt for an unanchored pattern fails when the cur-
-        after the CRLF.
+        rent position is at a  CRLF  sequence,  and  the  pattern  contains  no
+        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
+        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.
+        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
+        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
+        is a valid newline sequence and explicit \r or \n escapes appear in the
+        pattern.
           PCRE_NOTBOL
-Line 1794 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 2056 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
           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
         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.c 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
+        There  are a number of optimizations that pcre_exec() uses at the start
+        of a match, in order to speed up the process. For  example,  if  it  is
+        known  that  a  match must start with a specific character, it searches
+        the subject for that character, and fails immediately if it cannot find
+        it,  without actually running the main matching function. When callouts
+        are in use, these optimizations can cause  them  to  be  skipped.  This
+        option  disables  the  "start-up" optimizations, causing performance to
+        suffer, but ensuring that the callouts do occur.
           PCRE_NO_UTF8_CHECK
         When PCRE_UTF8 is set at compile time, the validity of the subject as a
         UTF-8  string is automatically checked when pcre_exec() is subsequently
         called.  The value of startoffset is also checked  to  ensure  that  it
-        points  to the start of a UTF-8 character. If an invalid UTF-8 sequence
+        points  to  the start of a UTF-8 character. There is a discussion about
-        of bytes is found, pcre_exec() returns the error PCRE_ERROR_BADUTF8. If
+        the validity of UTF-8 strings in the section on UTF-8  support  in  the
-        startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is
+        main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,
-        returned.
+        pcre_exec() returns the error PCRE_ERROR_BADUTF8. If  startoffset  con-
+        tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
-        If you already know that your subject is valid, and you  want  to  skip
-        these    checks    for   performance   reasons,   you   can   set   the
+        If  you  already  know that your subject is valid, and you want to skip
-        PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to
+        these   checks   for   performance   reasons,   you   can    set    the
-        do  this  for the second and subsequent calls to pcre_exec() if you are
+        PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to
-        making repeated calls to find all  the  matches  in  a  single  subject
+        do this for the second and subsequent calls to pcre_exec() if  you  are
-        string.  However,  you  should  be  sure  that the value of startoffset
+        making  repeated  calls  to  find  all  the matches in a single subject
-        points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is
+        string. However, you should be  sure  that  the  value  of  startoffset
-        set,  the  effect of passing an invalid UTF-8 string as a subject, or a
+        points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is
-        value of startoffset that does not point to the start of a UTF-8  char-
+        set, the effect of passing an invalid UTF-8 string as a subject,  or  a
+        value  of startoffset that does not point to the start of a UTF-8 char-
         acter, is undefined. Your program may crash.
-          PCRE_PARTIAL
+          PCRE_PARTIAL_HARD
+          PCRE_PARTIAL_SOFT
-        This  option  turns  on  the  partial  matching feature. If the subject
+        These options turn on the partial matching feature. For backwards  com-
-        string fails to match the pattern, but at some point during the  match-
+        patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial
-        ing  process  the  end of the subject was reached (that is, the subject
+        match occurs if the end of the subject string is reached  successfully,
-        partially matches the pattern and the failure to  match  occurred  only
+        but  there  are not enough subject characters to complete the match. If
-        because  there were not enough subject characters), pcre_exec() returns
+        this happens when PCRE_PARTIAL_HARD  is  set,  pcre_exec()  immediately
-        PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is
+        returns  PCRE_ERROR_PARTIAL.  Otherwise,  if  PCRE_PARTIAL_SOFT is set,
-        used,  there  are restrictions on what may appear in the pattern. These
+        matching continues by testing any other alternatives. Only if they  all
-        are discussed in the pcrepartial documentation.
+        fail  is  PCRE_ERROR_PARTIAL  returned (instead of PCRE_ERROR_NOMATCH).
+        The portion of the string that was inspected when the partial match was
+        found  is  set  as  the first matching string. There is a more detailed
+        discussion in the pcrepartial documentation.
     The string to be matched by pcre_exec()
         The subject string is passed to pcre_exec() as a pointer in subject,  a
-        length  in  length, and a starting byte offset in startoffset. In UTF-8
+        length (in bytes) in length, and a starting byte offset in startoffset.
-        mode, the byte offset must point to the start  of  a  UTF-8  character.
+        In UTF-8 mode, the byte offset must point to the start of a UTF-8 char-
-        Unlike  the  pattern string, the subject may contain binary zero bytes.
+        acter.  Unlike  the pattern string, the subject may contain binary zero
-        When the starting offset is zero, the search for a match starts at  the
+        bytes. When the starting offset is zero, the search for a match  starts
-        beginning of the subject, and this is by far the most common case.
+        at  the  beginning  of  the subject, and this is by far the most common
+        case.
-        A  non-zero  starting offset is useful when searching for another match
-        in the same subject by calling pcre_exec() again after a previous  suc-
+        A non-zero starting offset is useful when searching for  another  match
-        cess.   Setting  startoffset differs from just passing over a shortened
+        in  the same subject by calling pcre_exec() again after a previous suc-
-        string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins
+        cess.  Setting startoffset differs from just passing over  a  shortened
+        string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins
         with any kind of lookbehind. For example, consider the pattern
           \Biss\B
-        which  finds  occurrences  of "iss" in the middle of words. (\B matches
+        which finds occurrences of "iss" in the middle of  words.  (\B  matches
-        only if the current position in the subject is not  a  word  boundary.)
+        only  if  the  current position in the subject is not a word boundary.)
-        When  applied  to the string "Mississipi" the first call to pcre_exec()
+        When applied to the string "Mississipi" the first call  to  pcre_exec()
-        finds the first occurrence. If pcre_exec() is called  again  with  just
+        finds  the  first  occurrence. If pcre_exec() is called again with just
-        the  remainder  of  the  subject,  namely  "issipi", it does not match,
+        the remainder of the subject,  namely  "issipi",  it  does  not  match,
         because \B is always false at the start of the subject, which is deemed
-        to  be  a  word  boundary. However, if pcre_exec() is passed the entire
+        to be a word boundary. However, if pcre_exec()  is  passed  the  entire
         string again, but with startoffset set to 4, it finds the second occur-
-        rence  of "iss" because it is able to look behind the starting point to
+        rence of "iss" because it is able to look behind the starting point  to
         discover that it is preceded by a letter.
-        If a non-zero starting offset is passed when the pattern  is  anchored,
+        If  a  non-zero starting offset is passed when the pattern is anchored,
         one attempt to match at the given offset is made. This can only succeed
-        if the pattern does not require the match to be at  the  start  of  the
+        if  the  pattern  does  not require the match to be at the start of the
         subject.
     How pcre_exec() returns captured substrings
-        In  general, a pattern matches a certain portion of the subject, and in
+        In general, a pattern matches a certain portion of the subject, and  in
-        addition, further substrings from the subject  may  be  picked  out  by
+        addition,  further  substrings  from  the  subject may be picked out by
-        parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,
+        parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
-        this is called "capturing" in what follows, and the  phrase  "capturing
+        this  is  called "capturing" in what follows, and the phrase "capturing
-        subpattern"  is  used for a fragment of a pattern that picks out a sub-
+        subpattern" is used for a fragment of a pattern that picks out  a  sub-
-        string. PCRE supports several other kinds of  parenthesized  subpattern
+        string.  PCRE  supports several other kinds of parenthesized subpattern
         that do not cause substrings to be captured.
-        Captured  substrings are returned to the caller via a vector of integer
+        Captured substrings are returned to the caller via a vector of integers
-        offsets whose address is passed in ovector. The number of  elements  in
+        whose  address is passed in ovector. The number of elements in the vec-
-        the  vector is passed in ovecsize, which must be a non-negative number.
+        tor is passed in ovecsize, which must be a non-negative  number.  Note:
-        Note: this argument is NOT the size of ovector in bytes.
+        this argument is NOT the size of ovector in bytes.
-        The first two-thirds of the vector is used to pass back  captured  sub-
+        The  first  two-thirds of the vector is used to pass back captured sub-
-        strings,  each  substring using a pair of integers. The remaining third
+        strings, each substring using a pair of integers. The  remaining  third
-        of the vector is used as workspace by pcre_exec() while  matching  cap-
+        of  the  vector is used as workspace by pcre_exec() while matching cap-
-        turing  subpatterns, and is not available for passing back information.
+        turing subpatterns, and is not available for passing back  information.
-        The length passed in ovecsize should always be a multiple of three.  If
+        The  number passed in ovecsize should always be a multiple of three. If
         it is not, it is rounded down.
-        When  a  match  is successful, information about captured substrings is
+        When a match is successful, information about  captured  substrings  is
-        returned in pairs of integers, starting at the  beginning  of  ovector,
+        returned  in  pairs  of integers, starting at the beginning of ovector,
-        and  continuing  up  to two-thirds of its length at the most. The first
+        and continuing up to two-thirds of its length at the  most.  The  first
-        element of a pair is set to the offset of the first character in a sub-
+        element  of  each pair is set to the byte offset of the first character
-        string,  and  the  second  is  set to the offset of the first character
+        in a substring, and the second is set to the byte offset of  the  first
-        after the end of a substring. The  first  pair,  ovector[0]  and  ovec-
+        character  after  the end of a substring. Note: these values are always
-        tor[1],  identify  the  portion  of  the  subject string matched by the
+        byte offsets, even in UTF-8 mode. They are not character counts.
-        entire pattern. The next pair is used for the first  capturing  subpat-
-        tern, and so on. The value returned by pcre_exec() is one more than the
+        The first pair of integers, ovector[0]  and  ovector[1],  identify  the
-        highest numbered pair that has been set. For example, if two substrings
+        portion  of  the subject string matched by the entire pattern. The next
-        have  been captured, the returned value is 3. If there are no capturing
+        pair is used for the first capturing subpattern, and so on.  The  value
-        subpatterns, the return value from a successful match is 1,  indicating
+        returned by pcre_exec() is one more than the highest numbered pair that
-        that just the first pair of offsets has been set.
+        has been set.  For example, if two substrings have been  captured,  the
+        returned  value is 3. If there are no capturing subpatterns, the return
+        value from a successful match is 1, indicating that just the first pair
+        of offsets has been set.
         If a capturing subpattern is matched repeatedly, it is the last portion
         of the string that it matched that is returned.
         If the vector is too small to hold all the captured substring  offsets,
         it is used as far as possible (up to two-thirds of its length), and the
-        function returns a value of zero. In particular, if the substring  off-
+        function returns a value of zero. If the substring offsets are  not  of
-        sets are not of interest, pcre_exec() may be called with ovector passed
+        interest,  pcre_exec()  may  be  called with ovector passed as NULL and
-        as NULL and ovecsize as zero. However, if  the  pattern  contains  back
+        ovecsize as zero. However, if the pattern contains back references  and
-        references  and  the  ovector is not big enough to remember the related
+        the  ovector is not big enough to remember the related substrings, PCRE
-        substrings, PCRE has to get additional memory for use during  matching.
+        has to get additional memory for use during matching. Thus it  is  usu-
-        Thus it is usually advisable to supply an ovector.
+        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 2020 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 2309 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
           PCRE_ERROR_BADPARTIAL     (-13)
-        The PCRE_PARTIAL option was used with  a  compiled  pattern  containing
+        This code is no longer in  use.  It  was  formerly  returned  when  the
-        items  that are not supported for partial matching. See the pcrepartial
+        PCRE_PARTIAL  option  was used with a compiled pattern containing items
-        documentation for details of partial matching.
+        that were  not  supported  for  partial  matching.  From  release  8.00
+        onwards, there are no restrictions on partial matching.
           PCRE_ERROR_INTERNAL       (-14)
-        An unexpected internal error has occurred. This error could  be  caused
+        An  unexpected  internal error has occurred. This error could be caused
         by a bug in PCRE or by overwriting of the compiled pattern.
           PCRE_ERROR_BADCOUNT       (-15)
-        This  error is given if the value of the ovecsize argument is negative.
+        This error is given if the value of the ovecsize argument is negative.
           PCRE_ERROR_RECURSIONLIMIT (-21)
-Line 2039 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 2329 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
         field  in  a  pcre_extra  structure (or defaulted) was reached. See the
         description above.
-          PCRE_ERROR_NULLWSLIMIT    (-22)
-        When a group that can match an empty  substring  is  repeated  with  an
-        unbounded  upper  limit, the subject position at the start of the group
-        must be remembered, so that a test for an empty string can be made when
-        the  end  of the group is reached. Some workspace is required for this;
-        if it runs out, this error is given.
           PCRE_ERROR_BADNEWLINE     (-23)
         An invalid combination of PCRE_NEWLINE_xxx options was given.
-        Error numbers -16 to -20 are not used by pcre_exec().
+        Error numbers -16 to -20 and -22 are not used by pcre_exec().
  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
-Line 2189 
 EXTRACTING CAPTURED SUBSTRINGS BY NAME
+Line 2471 
 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 subpat-
+        terns  with  the  same number, as described in the section on duplicate
+        subpattern numbers in the pcrepattern page, you  cannot  use  names  to
+        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 2196 
 DUPLICATE SUBPATTERN NAMES
+Line 2486 
 DUPLICATE SUBPATTERN NAMES
              const char *name, char **first, char **last);
         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. When duplicates are present, pcre_copy_named_substring() and
+        use the same names.)
+        Normally, patterns with duplicate names are such that in any one match,
+        only  one of the named subpatterns participates. An example is shown in
+        the pcrepattern documentation.
+        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,  an  empty  string  is
+        the given name that is set. If  none  are  set,  PCRE_ERROR_NOSUBSTRING
-        returned.  The pcre_get_stringnumber() function returns one of the num-
+        (-7)  is  returned;  no  data  is returned. The pcre_get_stringnumber()
-        bers that are associated with the name, but it is not defined which  it
+        function returns one of the numbers that are associated with the  name,
-        is.
+        but it is not defined which it is.
         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
-Line 2250 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
+Line 2546 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
         characteristics  to  the  normal  algorithm, and is not compatible with
         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
-        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
+        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-
-        ent  way,  and  this is described below. The other common arguments are
+        ent way, and this is described below. The other  common  arguments  are
-        used in the same way as for pcre_exec(), so their  description  is  not
+        used  in  the  same way as for pcre_exec(), so their description is not
         repeated here.
-        The  two  additional  arguments provide workspace for the function. The
+        The two additional arguments provide workspace for  the  function.  The
-        workspace vector should contain at least 20 elements. It  is  used  for
+        workspace  vector  should  contain at least 20 elements. It is used for
         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
-        workspace will be needed for patterns and subjects where  there  are  a
+        workspace  will  be  needed for patterns and subjects where there are a
         lot of potential matches.
         Here is an example of a simple call to pcre_dfa_exec():
-Line 2284 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
+Line 2581 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
     Option bits for pcre_dfa_exec()
-        The  unused  bits  of  the options argument for pcre_dfa_exec() must be
+        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-
+        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, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last
+        PCRE_NOTEMPTY_ATSTART, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, PCRE_PAR-
-        three of these are the same as for pcre_exec(), so their description is
+        TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All  but  the  last
-        not repeated here.
+        four  of  these  are  exactly  the  same  as  for pcre_exec(), so their
+        description is not repeated here.
-          PCRE_PARTIAL
+          PCRE_PARTIAL_HARD
-        This has the same general effect as it does for  pcre_exec(),  but  the
+          PCRE_PARTIAL_SOFT
-        details   are   slightly   different.  When  PCRE_PARTIAL  is  set  for
-        pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is  converted  into
+        These have the same general effect as they do for pcre_exec(), but  the
-        PCRE_ERROR_PARTIAL  if  the  end  of the subject is reached, there have
+        details  are  slightly  different.  When  PCRE_PARTIAL_HARD  is set for
-        been no complete matches, but there is still at least one matching pos-
+        pcre_dfa_exec(), it returns PCRE_ERROR_PARTIAL if the end of  the  sub-
-        sibility.  The portion of the string that provided the partial match is
+        ject  is  reached  and there is still at least one matching possibility
-        set as the first matching string.
+        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
+        there is still at least one matching possibility. The  portion  of  the
+        string  that  was inspected when the longest partial match was found is
+        set as the first matching string in both cases.
           PCRE_DFA_SHORTEST
-Line 2310 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
+Line 2613 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
           PCRE_DFA_RESTART
-        When  pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option, and
+        When pcre_dfa_exec() returns a partial match, it is possible to call it
-        returns a partial match, it is possible to call it  again,  with  addi-
+        again, with additional subject characters, and have  it  continue  with
-        tional  subject  characters,  and have it continue with the same match.
+        the  same match. The PCRE_DFA_RESTART option requests this action; when
-        The PCRE_DFA_RESTART option requests this action; when it is  set,  the
+        it is set, the workspace and wscount options must  reference  the  same
-        workspace  and wscount options must reference the same vector as before
+        vector  as  before  because data about the match so far is left in them
-        because data about the match so far is left in  them  after  a  partial
+        after a partial match. There is more discussion of this facility in the
-        match.  There  is  more  discussion of this facility in the pcrepartial
+        pcrepartial documentation.
-        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 2339 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
+Line 2641 
 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).
+        tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
  AUTHOR
-Line 2406 
 AUTHOR
+Line 2708 
 AUTHOR
  REVISION
-        Last updated: 04 June 2007
+        Last updated: 03 October 2009
-        Copyright (c) 1997-2007 University of Cambridge.
+        Copyright (c) 1997-2009 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 2436 
 PCRE CALLOUTS
+Line 2738 
 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 2458 
 PCRE CALLOUTS
+Line 2760 
 PCRE CALLOUTS
  MISSING CALLOUTS
         You  should  be  aware  that,  because of optimizations in the way PCRE
-        matches patterns, callouts sometimes do not happen. For example, if the
+        matches patterns by default, callouts  sometimes  do  not  happen.  For
-        pattern is
+        example, if the pattern is
           ab(?C4)cd
-Line 2468 
 MISSING CALLOUTS
+Line 2770 
 MISSING CALLOUTS
         ever  start,  and  the  callout is never reached. However, with "abyd",
         though the result is still no match, the callout is obeyed.
+        If the pattern is studied, PCRE knows the minimum length of a  matching
+        string,  and will immediately give a "no match" return without actually
+        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
-Line 2495 
 THE CALLOUT INTERFACE
+Line 2807 
 THE CALLOUT INTERFACE
         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 2577 
 AUTHOR
+Line 2889 
 AUTHOR
  REVISION
-        Last updated: 29 May 2007
+        Last updated: 29 September 2009
-        Copyright (c) 1997-2007 University of Cambridge.
+        Copyright (c) 1997-2009 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 2592 
 NAME
+Line 2904 
 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 version 7.0 contains some fea-
+        respect to Perl 5.10.
-        tures that are expected to be in the forthcoming 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 2641 
 DIFFERENCES BETWEEN PCRE AND PERL
+Line 2956 
 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 provides some extensions to the Perl regular expression facil-
+.  PCRE  does  support  Perl  5.10's  backtracking  verbs  (*ACCEPT),
-        ities.   Perl  5.10  will  include new features that are not in earlier
+        (*FAIL), (*F), (*COMMIT), (*PRUNE), (*SKIP), and (*THEN), but  only  in
-        versions, some of which (such as named parentheses) have been  in  PCRE
+        the forms without an argument. PCRE does not support (*MARK).
-        for some time. This list is with respect to Perl 5.10:
+.  PCRE's handling of duplicate subpattern numbers and duplicate sub-
-        (a)  Although  lookbehind  assertions  must match fixed length strings,
+        pattern names is not as general as Perl's. This is a consequence of the
-        each alternative branch of a lookbehind assertion can match a different
+        fact the PCRE works internally just with numbers, using an external ta-
-        length of string. Perl requires them all to have the same length.
+        ble to translate between numbers and names. In  particular,  a  pattern
+        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  includes new features that are not in earlier ver-
+        sions of Perl, some of which (such as named parentheses) have  been  in
+        PCRE for some time. This list is with respect to Perl 5.10:
+        (a)  Although  lookbehind  assertions  in  PCRE must match fixed length
+        strings, each alternative branch of a lookbehind assertion can match  a
+        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
+        cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
-        ignored. (Perl can be made to issue a warning.)
+        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.
-        (g) The callout facility is PCRE-specific.
+        (h) The callout facility is PCRE-specific.
-        (h) The partial matching facility is PCRE-specific.
+        (i) The partial matching facility is PCRE-specific.
-        (i) Patterns compiled by PCRE can be saved and re-used at a later time,
+        (j) Patterns compiled by PCRE can be saved and re-used at a later time,
         even on different hosts that have the other endianness.
-        (j)  The  alternative  matching function (pcre_dfa_exec()) matches in a
+        (k) The alternative matching function (pcre_dfa_exec())  matches  in  a
         different way and is not Perl-compatible.
+        (l)  PCRE  recognizes some special sequences such as (*CR) at the start
+        of a pattern that set overall options that cannot be changed within the
+        pattern.
  AUTHOR
-Line 2705 
 AUTHOR
+Line 3046 
 AUTHOR
  REVISION
-        Last updated: 06 March 2007
+        Last updated: 04 October 2009
-        Copyright (c) 1997-2007 University of Cambridge.
+        Copyright (c) 1997-2009 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 2719 
 NAME
+Line 3060 
 NAME
  PCRE REGULAR EXPRESSION DETAILS
-        The  syntax  and semantics of the regular expressions supported by PCRE
+        The  syntax and semantics of the regular expressions that are supported
-        are described below. Regular expressions are also described in the Perl
+        by PCRE are described in detail below. There is a quick-reference  syn-
-        documentation  and  in  a  number  of books, some of which have copious
+        tax summary in the pcresyntax page. PCRE tries to match Perl syntax and
-        examples.  Jeffrey Friedl's "Mastering Regular Expressions",  published
+        semantics as closely as it can. PCRE  also  supports  some  alternative
-        by  O'Reilly, covers regular expressions in great detail. This descrip-
+        regular  expression  syntax (which does not conflict with the Perl syn-
-        tion of PCRE's regular expressions is intended as reference material.
+        tax) in order to provide some compatibility with regular expressions in
+        Python, .NET, and Oniguruma.
+        Perl's  regular expressions are described in its own documentation, and
+        regular expressions in general are covered in a number of  books,  some
+        of  which  have  copious  examples. Jeffrey Friedl's "Mastering Regular
+        Expressions", published by  O'Reilly,  covers  regular  expressions  in
+        great  detail.  This  description  of  PCRE's  regular  expressions  is
+        intended as reference material.
         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.  How this affects pattern
+        pcre_compile()  or  pcre_compile2() with the PCRE_UTF8 option. There is
-        matching is mentioned in several places below. There is also a  summary
+        also a special sequence that can be given at the start of a pattern:
-        of  UTF-8  features  in  the  section on UTF-8 support in the main pcre
-        page.
+          (*UTF8)
+        Starting a pattern with this sequence  is  equivalent  to  setting  the
+        PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting
+        UTF-8 mode affects pattern matching  is  mentioned  in  several  places
+        below.  There  is  also  a  summary of UTF-8 features in the section on
+        UTF-8 support in the main pcre page.
         The remainder of this document discusses the  patterns  that  are  sup-
         ported  by  PCRE when its main matching function, pcre_exec(), is used.
-Line 2744 
 PCRE REGULAR EXPRESSION DETAILS
+Line 3099 
 PCRE REGULAR EXPRESSION DETAILS
         discussed in the pcrematching page.
+ NEWLINE CONVENTIONS
+        PCRE  supports five different conventions for indicating line breaks in
+        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 pcreapi page  has  further
+        discussion  about newlines, and shows how to set the newline convention
+        in the options arguments for the compiling and matching functions.
+        It is also possible to specify a newline convention by starting a  pat-
+        tern string with one of the following five sequences:
+          (*CR)        carriage return
+          (*LF)        linefeed
+          (*CRLF)      carriage return, followed by linefeed
+          (*ANYCRLF)   any of the three above
+          (*ANY)       all Unicode newline sequences
+        These  override  the default and the options given to pcre_compile() or
+        pcre_compile2(). For example, on a Unix system where LF is the  default
+        newline sequence, the pattern
+          (*CR)a.b
+        changes the convention to CR. That pattern matches "a\nb" because LF is
+        no longer a newline. Note that these special settings,  which  are  not
+        Perl-compatible,  are  recognized  only at the very start of a pattern,
+        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
+        matches. By default, this is any Unicode  newline  sequence,  for  Perl
+        compatibility.  However, this can be changed; see the description of \R
+        in the section entitled "Newline sequences" below. A change of \R  set-
+        ting can be combined with a change of newline convention.
  CHARACTERS AND METACHARACTERS
         A  regular  expression  is  a pattern that is matched against a subject
-Line 2799 
 CHARACTERS AND METACHARACTERS
+Line 3191 
 CHARACTERS AND METACHARACTERS
                    syntax)
           ]      terminates the character class
-        The  following sections describe the use of each of the metacharacters.
+        The following sections describe the use of each of the metacharacters.
  BACKSLASH
         The backslash character has several uses. Firstly, if it is followed by
-        a  non-alphanumeric  character,  it takes away any special meaning that
+        a non-alphanumeric character, it takes away any  special  meaning  that
-        character may have. This  use  of  backslash  as  an  escape  character
+        character  may  have.  This  use  of  backslash  as an escape character
         applies both inside and outside character classes.
-        For  example,  if  you want to match a * character, you write \* in the
+        For example, if you want to match a * character, you write  \*  in  the
-        pattern.  This escaping action applies whether  or  not  the  following
+        pattern.   This  escaping  action  applies whether or not the following
-        character  would  otherwise be interpreted as a metacharacter, so it is
+        character would otherwise be interpreted as a metacharacter, so  it  is
-        always safe to precede a non-alphanumeric  with  backslash  to  specify
+        always  safe  to  precede  a non-alphanumeric with backslash to specify
-        that  it stands for itself. In particular, if you want to match a back-
+        that it stands for itself. In particular, if you want to match a  back-
         slash, you write \\.
-        If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in
+        If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in
-        the  pattern (other than in a character class) and characters between a
+        the pattern (other than in a character class) and characters between  a
         # outside a character class and the next newline are ignored. An escap-
-        ing  backslash  can  be  used to include a whitespace or # character as
+        ing backslash can be used to include a whitespace  or  #  character  as
         part of the pattern.
-        If you want to remove the special meaning from a  sequence  of  charac-
+        If  you  want  to remove the special meaning from a sequence of charac-
-        ters,  you can do so by putting them between \Q and \E. This is differ-
+        ters, you can do so by putting them between \Q and \E. This is  differ-
-        ent from Perl in that $ and  @  are  handled  as  literals  in  \Q...\E
+        ent  from  Perl  in  that  $  and  @ are handled as literals in \Q...\E
-        sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-
+        sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-
         tion. Note the following examples:
           Pattern            PCRE matches   Perl matches
-Line 2835 
 BACKSLASH
+Line 3227 
 BACKSLASH
           \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.
     Non-printing characters
         A second use of backslash provides a way of encoding non-printing char-
-        acters in patterns in a visible manner. There is no restriction on  the
+        acters  in patterns in a visible manner. There is no restriction on the
-        appearance  of non-printing characters, apart from the binary zero that
+        appearance of non-printing characters, apart from the binary zero  that
-        terminates a pattern, but when a pattern  is  being  prepared  by  text
+        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)
           \cx       "control-x", where x is any character
           \e        escape (hex 1B)
           \f        formfeed (hex 0C)
-          \n        newline (hex 0A)
+          \n        linefeed (hex 0A)
           \r        carriage return (hex 0D)
           \t        tab (hex 09)
           \ddd      character with octal code ddd, or backreference
           \xhh      character with hex code hh
           \x{hhh..} character with hex code hhh..
-        The precise effect of \cx is as follows: if x is a lower  case  letter,
+        The  precise  effect of \cx is as follows: if x is a lower case letter,
-        it  is converted to upper case. Then bit 6 of the character (hex 40) is
+        it is converted to upper case. Then bit 6 of the character (hex 40)  is
-        inverted.  Thus \cz becomes hex 1A, but \c{ becomes hex 3B,  while  \c;
+        inverted.   Thus  \cz becomes hex 1A, but \c{ becomes hex 3B, while \c;
         becomes hex 7B.
-        After  \x, from zero to two hexadecimal digits are read (letters can be
+        After \x, from zero to two hexadecimal digits are read (letters can  be
-        in upper or lower case). Any number of hexadecimal  digits  may  appear
+        in  upper  or  lower case). Any number of hexadecimal digits may appear
-        between  \x{  and  },  but the value of the character code must be less
+        between \x{ and }, but the value of the character  code  must  be  less
-        than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode (that is,
+        than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,
-        the  maximum  hexadecimal  value is 7FFFFFFF). If characters other than
+        the maximum value in hexadecimal is 7FFFFFFF. Note that this is  bigger
-        hexadecimal digits appear between \x{ and }, or if there is  no  termi-
+        than the largest Unicode code point, which is 10FFFF.
-        nating  }, this form of escape is not recognized.  Instead, the initial
-        \x will be interpreted as a basic hexadecimal escape, with no following
+        If  characters  other than hexadecimal digits appear between \x{ and },
-        digits, giving a character whose value is zero.
+        or if there is no terminating }, this form of escape is not recognized.
+        Instead,  the  initial  \x  will  be interpreted as a basic hexadecimal
+        escape, with no following digits, giving a  character  whose  value  is
+        zero.
         Characters whose value is less than 256 can be defined by either of the
         two syntaxes for \x. There is no difference in the way  they  are  han-
-Line 2926 
 BACKSLASH
+Line 3321 
 BACKSLASH
     Absolute and relative back references
-        The  sequence  \g followed by a positive or negative number, optionally
+        The  sequence  \g followed by an unsigned or a negative number, option-
-        enclosed in braces, is an absolute or relative back reference. A  named
+        ally enclosed in braces, is an absolute or relative back  reference.  A
-        back  reference can be coded as \g{name}. Back references are discussed
+        named back reference can be coded as \g{name}. Back references are dis-
-        later, following the discussion of parenthesized subpatterns.
+        cussed later, following the discussion of parenthesized subpatterns.
+    Absolute and relative subroutine calls
+        For compatibility with Oniguruma, the non-Perl syntax \g followed by  a
+        name or a number enclosed either in angle brackets or single quotes, is
+        an alternative syntax for referencing a subpattern as  a  "subroutine".
+        Details  are  discussed  later.   Note  that  \g{...} (Perl syntax) and
+        \g<...> (Oniguruma syntax) are not synonymous. The  former  is  a  back
+        reference; the latter is a subroutine call.
     Generic character types
-Line 2938 
 BACKSLASH
+Line 3342 
 BACKSLASH
           \d     any decimal digit
           \D     any character that is not a decimal digit
+          \h     any horizontal whitespace character
+          \H     any character that is not a horizontal whitespace character
           \s     any whitespace character
           \S     any character that is not a whitespace character
+          \v     any vertical whitespace character
+          \V     any character that is not a vertical whitespace character
           \w     any "word" character
           \W     any "non-word" character
         Each pair of escape sequences partitions the complete set of characters
-        into two disjoint sets. Any given character matches one, and only  one,
+        into  two disjoint sets. Any given character matches one, and only one,
         of each pair.
         These character type sequences can appear both inside and outside char-
-        acter classes. They each match one character of the  appropriate  type.
+        acter  classes.  They each match one character of the appropriate type.
-        If  the current matching point is at the end of the subject string, all
+        If the current matching point is at the end of the subject string,  all
         of them fail, since there is no character to match.
-        For compatibility with Perl, \s does not match the VT  character  (code
+        For  compatibility  with Perl, \s does not match the VT character (code
-).   This makes it different from the the POSIX "space" class. The \s
+).  This makes it different from the the POSIX "space" class. The  \s
-        characters are HT (9), LF (10), FF (12), CR (13), and space  (32).  (If
+        characters  are  HT  (9), LF (10), FF (12), CR (13), and space (32). If
         "use locale;" is included in a Perl script, \s may match the VT charac-
-        ter. In PCRE, it never does.)
+        ter. In PCRE, it never does.
+        In  UTF-8 mode, characters with values greater than 128 never match \d,
+        \s, or \w, and always match \D, \S, and \W. This is true even when Uni-
+        code  character  property  support is available. These sequences retain
+        their original meanings from before UTF-8 support was available, mainly
+        for  efficiency  reasons. Note that this also affects \b, because it is
+        defined in terms of \w and \W.
+        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
+        UTF-8 mode.  The horizontal space characters are:
+          U+0009     Horizontal tab
+          U+0020     Space
+          U+00A0     Non-break space
+          U+1680     Ogham space mark
+          U+180E     Mongolian vowel separator
+          U+2000     En quad
+          U+2001     Em quad
+          U+2002     En space
+          U+2003     Em space
+          U+2004     Three-per-em space
+          U+2005     Four-per-em space
+          U+2006     Six-per-em space
+          U+2007     Figure space
+          U+2008     Punctuation space
+          U+2009     Thin space
+          U+200A     Hair space
+          U+202F     Narrow no-break space
+          U+205F     Medium mathematical space
+          U+3000     Ideographic space
+        The vertical space characters are:
+          U+000A     Linefeed
+          U+000B     Vertical tab
+          U+000C     Formfeed
+          U+000D     Carriage return
+          U+0085     Next line
+          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-
-Line 2964 
 BACKSLASH
+Line 3413 
 BACKSLASH
         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.
+        are used for accented letters, and these are matched by \w. The use  of
+        locales with Unicode is discouraged.
-        In UTF-8 mode, characters with values greater than 128 never match  \d,
-        \s, or \w, and always match \D, \S, and \W. This is true even when Uni-
-        code character property support is available. The use of  locales  with
-        Unicode is discouraged.
     Newline sequences
-        Outside  a  character class, the escape sequence \R matches any Unicode
+        Outside  a  character class, by default, the escape sequence \R matches
-        newline sequence. This is an extension to Perl. In non-UTF-8 mode \R is
+        any Unicode newline sequence. This is a Perl 5.10 feature. In non-UTF-8
-        equivalent to the following:
+        mode \R is equivalent to the following:
           (?>\r\n|\n|\x0b|\f|\r|\x85)
-Line 2991 
 BACKSLASH
+Line 3436 
 BACKSLASH
         rator, U+2029).  Unicode character property support is not  needed  for
         these characters to be recognized.
+        It is possible to restrict \R to match only CR, LF, or CRLF (instead of
+        the complete set  of  Unicode  line  endings)  by  setting  the  option
+        PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
+        (BSR is an abbrevation for "backslash R".) This can be made the default
+        when  PCRE  is  built;  if this is the case, the other behaviour can be
+        requested via the PCRE_BSR_UNICODE option.   It  is  also  possible  to
+        specify  these  settings  by  starting a pattern string with one of the
+        following sequences:
+          (*BSR_ANYCRLF)   CR, LF, or CRLF only
+          (*BSR_UNICODE)   any Unicode newline sequence
+        These override the default and the options given to  pcre_compile()  or
+        pcre_compile2(),  but  they  can  be  overridden  by  options  given to
+        pcre_exec() or pcre_dfa_exec(). Note that these special settings, which
+        are  not  Perl-compatible,  are  recognized only at the very start of a
+        pattern, and that they must be in upper case. If more than one of  them
+        is present, the last one is used. They can be combined with a change of
+        newline convention, for example, a pattern can start with:
+          (*ANY)(*BSR_ANYCRLF)
         Inside a character class, \R matches the letter "R".
     Unicode character properties
         When PCRE is built with Unicode character property support, three addi-
-        tional escape sequences to match  character  properties  are  available
+        tional  escape sequences that match characters with specific properties
-        when UTF-8 mode is selected. They are:
+        are available.  When not in UTF-8 mode, these sequences are  of  course
+        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
         any character (including newline). Other properties such as "InMusical-
-        Symbols" are not currently supported by PCRE. Note  that  \P{Any}  does
+        Symbols"  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.
+        A  character from one of these sets can be matched using a script name.
         For example:
           \p{Greek}
           \P{Han}
-        Those  that are not part of an identified script are lumped together as
+        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,
-        Buhid,   Canadian_Aboriginal,   Cherokee,  Common,  Coptic,  Cuneiform,
+        Buhid,  Canadian_Aboriginal,  Cherokee,  Common,   Coptic,   Cuneiform,
         Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,
-        Gothic,  Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hira-
+        Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew,  Hira-
-        gana, Inherited, Kannada,  Katakana,  Kharoshthi,  Khmer,  Lao,  Latin,
+        gana,  Inherited,  Kannada,  Katakana,  Kharoshthi,  Khmer, Lao, Latin,
         Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,
-        Ogham, Old_Italic, Old_Persian, Oriya, Osmanya,  Phags_Pa,  Phoenician,
+        Ogham,  Old_Italic,  Old_Persian, Oriya, Osmanya, Phags_Pa, Phoenician,
         Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,
         Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.
-        Each character has exactly one general category property, specified  by
+        Each  character has exactly one general category property, specified by
         a two-letter abbreviation. For compatibility with Perl, negation can be
-        specified by including a circumflex between the opening brace  and  the
+        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
+        eral  category properties that start with that letter. In this case, in
-        the  absence of negation, the curly brackets in the escape sequence are
+        the absence of negation, the curly brackets in the escape sequence  are
         optional; these two examples have the same effect:
           \p{L}
-Line 3088 
 BACKSLASH
+Line 3557 
 BACKSLASH
           Zp    Paragraph separator
           Zs    Space separator
-        The special property L& is also supported: it matches a character  that
+        The  special property L& is also supported: it matches a character that
-        has  the  Lu,  Ll, or Lt property, in other words, a letter that is not
+        has the Lu, Ll, or Lt property, in other words, a letter  that  is  not
         classified as a modifier or "other".
-        The long synonyms for these properties  that  Perl  supports  (such  as
+        The  Cs  (Surrogate)  property  applies only to characters in the range
-        \p{Letter})  are  not  supported by PCRE, nor is it permitted to prefix
+        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). Perl does not support the Cs property.
+        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".
         No character that is in the Unicode table has the Cn (unassigned) prop-
         erty.  Instead, this property is assumed for any code point that is not
         in the Unicode table.
-        Specifying caseless matching does not affect  these  escape  sequences.
+        Specifying  caseless  matching  does not affect these escape sequences.
         For example, \p{Lu} always matches only upper case letters.
-        The  \X  escape  matches  any number of Unicode characters that form an
+        The \X escape matches any number of Unicode  characters  that  form  an
         extended Unicode sequence. \X is equivalent to
           (?>\PM\pM*)
-        That is, it matches a character without the "mark"  property,  followed
+        That  is,  it matches a character without the "mark" property, followed
-        by  zero  or  more  characters with the "mark" property, and treats the
+        by zero or more characters with the "mark"  property,  and  treats  the
-        sequence as an atomic group (see below).  Characters  with  the  "mark"
+        sequence  as  an  atomic group (see below).  Characters with the "mark"
-        property are typically accents that affect the preceding character.
+        property are typically accents that  affect  the  preceding  character.
+        None  of  them  have  codepoints less than 256, so in non-UTF-8 mode \X
+        matches any one character.
-        Matching  characters  by Unicode property is not fast, because PCRE has
+        Matching characters by Unicode property is not fast, because  PCRE  has
-        to search a structure that contains  data  for  over  fifteen  thousand
+        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.
     Resetting the match start
         The escape sequence \K, which is a Perl 5.10 feature, causes any previ-
-        ously  matched  characters  not  to  be  included  in the final matched
+        ously matched characters not  to  be  included  in  the  final  matched
         sequence. For example, the pattern:
           foo\Kbar
-        matches "foobar", but reports that it has matched "bar".  This  feature
+        matches  "foobar",  but reports that it has matched "bar". This feature
-        is  similar  to  a lookbehind assertion (described below).  However, in
+        is similar to a lookbehind assertion (described  below).   However,  in
-        this case, the part of the subject before the real match does not  have
+        this  case, the part of the subject before the real match does not have
-        to  be of fixed length, as lookbehind assertions do. The use of \K does
+        to be of fixed length, as lookbehind assertions do. The use of \K  does
-        not interfere with the setting of captured  substrings.   For  example,
+        not  interfere  with  the setting of captured substrings.  For example,
         when the pattern
           (foo)\Kbar
-Line 3139 
 BACKSLASH
+Line 3616 
 BACKSLASH
     Simple assertions
-        The  final use of backslash is for certain simple assertions. An asser-
+        The final use of backslash is for certain simple assertions. An  asser-
-        tion specifies a condition that has to be met at a particular point  in
+        tion  specifies a condition that has to be met at a particular point in
-        a  match, without consuming any characters from the subject string. The
+        a match, without consuming any characters from the subject string.  The
-        use of subpatterns for more complicated assertions is described  below.
+        use  of subpatterns for more complicated assertions is described below.
         The backslashed assertions are:
           \b     matches at a word boundary
-Line 3153 
 BACKSLASH
+Line 3630 
 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
+        These assertions may not appear in character classes (but note that  \b
         has a different meaning, namely the backspace character, inside a char-
         acter class).
-        A  word  boundary is a position in the subject string where the current
+        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.
+        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
+        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.
+        string if the first or last character matches \w, respectively. Neither
+        PCRE nor Perl has a separte "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 3286 
 SQUARE BRACKETS AND CHARACTER CLASSES
+Line 3766 
 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 3302 
 SQUARE BRACKETS AND CHARACTER CLASSES
+Line 3784 
 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 3318 
 SQUARE BRACKETS AND CHARACTER CLASSES
+Line 3800 
 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 3420 
 POSIX CHARACTER CLASSES
+Line 3902 
 POSIX CHARACTER CLASSES
  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.
+        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
-        PCRE_EXTENDED options can be changed  from  within  the  pattern  by  a
+        PCRE_EXTENDED options (which are Perl-compatible) can be  changed  from
-        sequence  of  Perl  option  letters  enclosed between "(?" and ")". The
+        within  the  pattern  by  a  sequence  of  Perl option letters enclosed
-        option letters are
+        between "(?" and ")".  The option letters are
           i  for PCRE_CASELESS
           m  for PCRE_MULTILINE
-Line 3452 
 INTERNAL OPTION SETTING
+Line 3934 
 INTERNAL OPTION SETTING
         is also permitted. If a  letter  appears  both  before  and  after  the
         hyphen, the option is unset.
-        When  an option change occurs at top level (that is, not inside subpat-
+        The  PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA
-        tern parentheses), the change applies to the remainder of  the  pattern
+        can be changed in the same way as the Perl-compatible options by  using
-        that follows.  If the change is placed right at the start of a pattern,
+        the characters J, U and X respectively.
-        PCRE extracts it into the global options (and it will therefore show up
-        in data extracted by the pcre_fullinfo() function).
+        When  one  of  these  option  changes occurs at top level (that is, not
+        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
         subpatterns) affects only that part of the current pattern that follows
-Line 3477 
 INTERNAL OPTION SETTING
+Line 3963 
 INTERNAL OPTION SETTING
         the  effects  of option settings happen at compile time. There would be
         some very weird behaviour otherwise.
-        The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and  PCRE_EXTRA
+        Note: There are other PCRE-specific options that  can  be  set  by  the
-        can  be changed in the same way as the Perl-compatible options by using
+        application  when  the  compile  or match functions are called. In some
-        the characters J, U and X respectively.
+        cases the pattern can contain special leading sequences such as (*CRLF)
+        to  override  what  the application has set or what has been defaulted.
+        Details are given in the section entitled  "Newline  sequences"  above.
+        There  is  also  the  (*UTF8)  leading sequence that can be used to set
+        UTF-8 mode; this is equivalent to setting the PCRE_UTF8 option.
  SUBPATTERNS
-Line 3537 
 SUBPATTERNS
+Line 4027 
 SUBPATTERNS
         "Saturday".
+ DUPLICATE SUBPATTERN NUMBERS
+        Perl 5.10 introduced a feature whereby each alternative in a subpattern
+        uses the same numbers for its capturing parentheses. Such a  subpattern
+        starts  with (?| and is itself a non-capturing subpattern. For example,
+        consider this pattern:
+          (?|(Sat)ur|(Sun))day
+        Because the two alternatives are inside a (?| group, both sets of  cap-
+        turing  parentheses  are  numbered one. Thus, when the pattern matches,
+        you can look at captured substring number  one,  whichever  alternative
+        matched.  This  construct  is useful when you want to capture part, but
+        not all, of one of a number of alternatives. Inside a (?| group, paren-
+        theses  are  numbered as usual, but the number is reset at the start of
+        each branch. The numbers of any capturing buffers that follow the  sub-
+        pattern  start after the highest number used in any branch. The follow-
+        ing example is taken from the Perl documentation.  The  numbers  under-
+        neath show in which buffer the captured content will be stored.
+          # before  ---------------branch-reset----------- after
+          / ( a )  (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x
+          # 1            2         2  3        2     3     4
+        A  backreference  to  a  numbered subpattern uses the most recent value
+        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
+        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
-Line 3563 
 NAMED SUBPATTERNS
+Line 4098 
 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 3576 
 NAMED SUBPATTERNS
+Line 4113 
 NAMED SUBPATTERNS
           (?<DN>Sat)(?:urday)?
         There  are  five capturing substrings, but only one is ever set after a
-        match.  The convenience  function  for  extracting  the  data  by  name
+        match.  (An alternative way of solving this problem is to use a "branch
-        returns  the  substring  for  the first (and in this example, the only)
+        reset" subpattern, as described in the previous section.)
-        subpattern of that name that matched.  This  saves  searching  to  find
-        which  numbered  subpattern  it  was. If you make a reference to a non-
+        The  convenience  function  for extracting the data by name returns the
-        unique named subpattern from elsewhere in the  pattern,  the  one  that
+        substring for the first (and in this example, the only)  subpattern  of
-        corresponds  to  the  lowest number is used. For further details of the
+        that  name  that  matched.  This saves searching to find which numbered
-        interfaces for handling named subpatterns, see the  pcreapi  documenta-
+        subpattern it was.
-        tion.
+        If you make a backreference to a non-unique named subpattern from else-
+        where  in the pattern, the one that corresponds to the first occurrence
+        of the name is used. In the absence of duplicate numbers (see the  pre-
+        vious  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 because PCRE uses only the numbers when
+        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 3600 
 REPETITION
+Line 4155 
 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 3625 
 REPETITION
+Line 4181 
 REPETITION
         the  syntax of a quantifier, is taken as a literal character. For exam-
         ple, {,6} is not a quantifier, but a literal string of four characters.
-        In  UTF-8  mode,  quantifiers  apply to UTF-8 characters rather than to
+        In UTF-8 mode, quantifiers apply to UTF-8  characters  rather  than  to
         individual bytes. Thus, for example, \x{100}{2} matches two UTF-8 char-
         acters, each of which is represented by a two-byte sequence. Similarly,
         when Unicode property support is available, \X{3} matches three Unicode
-        extended  sequences,  each of which may be several bytes long (and they
+        extended sequences, each of which may be several bytes long  (and  they
         may be of different lengths).
         The quantifier {0} is permitted, causing the expression to behave as if
-        the previous item and the quantifier were not present.
+        the previous item and the quantifier were not present. This may be use-
+        ful  for  subpatterns that are referenced as subroutines from elsewhere
+        in the pattern. Items other than subpatterns that have a {0} quantifier
+        are omitted from the compiled pattern.
         For  convenience, the three most common quantifiers have single-charac-
         ter abbreviations:
-Line 3763 
 ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
+Line 4322 
 ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
           (?>\d+)foo
-        This  kind  of  parenthesis "locks up" the  part of the pattern it con-
+        This kind of parenthesis "locks up" the  part of the  pattern  it  con-
-        tains once it has matched, and a failure further into  the  pattern  is
+        tains  once  it  has matched, and a failure further into the pattern is
-        prevented  from  backtracking into it. Backtracking past it to previous
+        prevented from backtracking into it. Backtracking past it  to  previous
         items, however, works as normal.
-        An alternative description is that a subpattern of  this  type  matches
+        An  alternative  description  is that a subpattern of this type matches
-        the  string  of  characters  that an identical standalone pattern would
+        the string of characters that an  identical  standalone  pattern  would
         match, if anchored at the current point in the subject string.
         Atomic grouping subpatterns are not capturing subpatterns. Simple cases
         such as the above example can be thought of as a maximizing repeat that
-        must swallow everything it can. So, while both \d+ and  \d+?  are  pre-
+        must  swallow  everything  it can. So, while both \d+ and \d+? are pre-
-        pared  to  adjust  the number of digits they match in order to make the
+        pared to adjust the number of digits they match in order  to  make  the
         rest of the pattern match, (?>\d+) can only match an entire sequence of
         digits.
-        Atomic  groups in general can of course contain arbitrarily complicated
+        Atomic groups in general can of course contain arbitrarily  complicated
-        subpatterns, and can be nested. However, when  the  subpattern  for  an
+        subpatterns,  and  can  be  nested. However, when the subpattern for an
         atomic group is just a single repeated item, as in the example above, a
-        simpler notation, called a "possessive quantifier" can  be  used.  This
+        simpler  notation,  called  a "possessive quantifier" can be used. This
-        consists  of  an  additional  + character following a quantifier. Using
+        consists of an additional + character  following  a  quantifier.  Using
         this notation, the previous example can be rewritten as
           \d++foo
+        Note that a possessive quantifier can be used with an entire group, for
+        example:
+          (abc|xyz){2,3}+
         Possessive  quantifiers  are  always  greedy;  the   setting   of   the
         PCRE_UNGREEDY option is ignored. They are a convenient notation for the
         simpler forms of atomic group. However, there is no difference  in  the
-Line 3831 
 ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
+Line 4395 
 ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
           ((?>\D+)|<\d+>)*[!?]
-        sequences  of non-digits cannot be broken, and failure happens quickly.
+        sequences of non-digits cannot be broken, and failure happens quickly.
  BACK REFERENCES
         Outside a character class, a backslash followed by a digit greater than
 (and possibly further digits) is a back reference to a capturing sub-
-        pattern earlier (that is, to its left) in the pattern,  provided  there
+        pattern  earlier  (that is, to its left) in the pattern, provided there
         have been that many previous capturing left parentheses.
         However, if the decimal number following the backslash is less than 10,
-        it is always taken as a back reference, and causes  an  error  only  if
+        it  is  always  taken  as a back reference, and causes an error only if
-        there  are  not that many capturing left parentheses in the entire pat-
+        there are not that many capturing left parentheses in the  entire  pat-
-        tern. In other words, the parentheses that are referenced need  not  be
+        tern.  In  other words, the parentheses that are referenced need not be
-        to  the left of the reference for numbers less than 10. A "forward back
+        to the left of the reference for numbers less than 10. A "forward  back
-        reference" of this type can make sense when a  repetition  is  involved
+        reference"  of  this  type can make sense when a repetition is involved
-        and  the  subpattern to the right has participated in an earlier itera-
+        and the subpattern to the right has participated in an  earlier  itera-
         tion.
-        It is not possible to have a numerical "forward back  reference"  to  a
+        It  is  not  possible to have a numerical "forward back reference" to a
-        subpattern  whose  number  is  10  or  more using this syntax because a
+        subpattern whose number is 10 or  more  using  this  syntax  because  a
-        sequence such as \50 is interpreted as a character  defined  in  octal.
+        sequence  such  as  \50 is interpreted as a character defined in octal.
         See the subsection entitled "Non-printing characters" above for further
-        details of the handling of digits following a backslash.  There  is  no
+        details  of  the  handling of digits following a backslash. There is no
-        such  problem  when named parentheses are used. A back reference to any
+        such problem when named parentheses are used. A back reference  to  any
         subpattern is possible using named parentheses (see below).
-        Another way of avoiding the ambiguity inherent in  the  use  of  digits
+        Another  way  of  avoiding  the ambiguity inherent in the use of digits
         following a backslash is to use the \g escape sequence, which is a fea-
-        ture introduced in Perl 5.10. This escape must be followed by  a  posi-
+        ture  introduced  in  Perl  5.10.  This  escape  must be followed by an
-        tive  or  a negative number, optionally enclosed in braces. These exam-
+        unsigned number or a negative number, optionally  enclosed  in  braces.
-        ples are all identical:
+        These examples are all identical:
           (ring), \1
           (ring), \g1
           (ring), \g{1}
-        A positive number specifies an absolute reference without the ambiguity
+        An  unsigned number specifies an absolute reference without the ambigu-
-        that  is  present  in  the older syntax. It is also useful when literal
+        ity that is present in the older syntax. It is also useful when literal
         digits follow the reference. A negative number is a relative reference.
         Consider this example:
           (abc(def)ghi)\g{-1}
         The sequence \g{-1} is a reference to the most recently started captur-
-        ing subpattern before \g, that is, is it equivalent to  \2.  Similarly,
+        ing  subpattern  before \g, that is, is it equivalent to \2. Similarly,
         \g{-2} would be equivalent to \1. The use of relative references can be
-        helpful in long patterns, and also in  patterns  that  are  created  by
+        helpful  in  long  patterns,  and  also in patterns that are created by
         joining together fragments that contain references within themselves.
-        A  back  reference matches whatever actually matched the capturing sub-
+        A back reference matches whatever actually matched the  capturing  sub-
-        pattern in the current subject string, rather  than  anything  matching
+        pattern  in  the  current subject string, rather than anything matching
         the subpattern itself (see "Subpatterns as subroutines" below for a way
         of doing that). So the pattern
           (sens|respons)e and \1ibility
-        matches "sense and sensibility" and "response and responsibility",  but
+        matches  "sense and sensibility" and "response and responsibility", but
-        not  "sense and responsibility". If caseful matching is in force at the
+        not "sense and responsibility". If caseful matching is in force at  the
-        time of the back reference, the case of letters is relevant. For  exam-
+        time  of the back reference, the case of letters is relevant. For exam-
         ple,
           ((?i)rah)\s+\1
-        matches  "rah  rah"  and  "RAH RAH", but not "RAH rah", even though the
+        matches "rah rah" and "RAH RAH", but not "RAH  rah",  even  though  the
         original capturing subpattern is matched caselessly.
-        There are several different ways of writing back  references  to  named
+        There  are  several  different ways of writing back references to named
-        subpatterns.  The  .NET syntax \k{name} and the Perl syntax \k<name> or
+        subpatterns. The .NET syntax \k{name} and the Perl syntax  \k<name>  or
-        \k'name' are supported, as is the Python syntax (?P=name). Perl  5.10's
+        \k'name'  are supported, as is the Python syntax (?P=name). Perl 5.10's
         unified back reference syntax, in which \g can be used for both numeric
-        and named references, is also supported. We  could  rewrite  the  above
+        and  named  references,  is  also supported. We could rewrite the above
         example in any of the following ways:
           (?<p1>(?i)rah)\s+\k<p1>
-Line 3910 
 BACK REFERENCES
+Line 4474 
 BACK REFERENCES
           (?P<p1>(?i)rah)\s+(?P=p1)
           (?<p1>(?i)rah)\s+\g{p1}
-        A  subpattern  that  is  referenced  by  name may appear in the pattern
+        A subpattern that is referenced by  name  may  appear  in  the  pattern
         before or after the reference.
-        There may be more than one back reference to the same subpattern. If  a
+        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
+        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
+        PCRE_EXTENDED option is set, this can be whitespace. Otherwise, the \g{
+        syntax or an empty comment (see "Comments" below) can be used.
         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
-Line 3988 
 ASSERTIONS
+Line 4555 
 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 4009 
 ASSERTIONS
+Line 4577 
 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 4037 
 ASSERTIONS
+Line 4604 
 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 4102 
 CONDITIONAL SUBPATTERNS
+Line 4673 
 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 4119 
 CONDITIONAL SUBPATTERNS
+Line 4690 
 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,