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-revision 91 by nigel,
Sat Feb 24 21:41:34 2007 UTC
+revision 93 by nigel,
Sat Feb 24 21:41:42 2007 UTC
 Line 18 
 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.  The current implementation of PCRE (release
+        just  a  few differences. (Certain features that appeared in Python and
-.x) corresponds approximately with Perl  5.8,  including  support  for
+        PCRE before they appeared in Perl are also available using  the  Python
-        UTF-8 encoded strings and Unicode general category properties. However,
+        syntax.)
-        this support has to be explicitly enabled; it is not the default.
+        The  current  implementation of PCRE (release 7.x) corresponds approxi-
-        In addition to the Perl-compatible matching function,  PCRE  also  con-
+        mately with Perl 5.10, including support for UTF-8 encoded strings  and
-        tains  an  alternative matching function that matches the same compiled
+        Unicode general category properties. However, UTF-8 and Unicode support
-        patterns in a different way. In certain circumstances, the  alternative
+        has to be explicitly enabled; it is not the default. The Unicode tables
-        function  has  some  advantages.  For  a discussion of the two matching
+        correspond to Unicode release 5.0.0.
-        algorithms, see the pcrematching page.
+        In  addition to the Perl-compatible matching function, PCRE contains an
-        PCRE is written in C and released as a C library. A  number  of  people
+        alternative matching function that matches the same  compiled  patterns
-        have  written  wrappers and interfaces of various kinds. In particular,
+        in  a different way. In certain circumstances, the alternative function
-        Google Inc.  have provided a comprehensive C++  wrapper.  This  is  now
+        has some advantages. For a discussion of the two  matching  algorithms,
+        see the 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,
+        Google  Inc.   have  provided  a comprehensive C++ wrapper. This is now
         included as part of the PCRE distribution. The pcrecpp page has details
-        of this interface. Other people's contributions can  be  found  in  the
+        of  this  interface.  Other  people's contributions can be found in the
         Contrib directory at the primary FTP site, which is:
         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
-        Details  of  exactly which Perl regular expression features are and are
+        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.
-        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  file
         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 are concatenated,  for  ease
         of searching. The sections are as follows:
           pcre              this document
-Line 84 
 USER DOCUMENTATION
+Line 89 
 USER DOCUMENTATION
           pcrestack         discussion of stack usage
           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 will be slower.
+        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. The  maxi-
-        mum compiled length of subpattern with  an  explicit  repeat  count  is
+        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 non-capturing subpatterns, but the
+        There is no limit to the number of parenthesized subpatterns, but there
-        maximum depth of nesting of  all  kinds  of  parenthesized  subpattern,
+        can be no more than 65535 capturing subpatterns.
-        including capturing subpatterns, assertions, and other types of subpat-
-        tern, is 200.
-        The maximum length of name for a named subpattern is 32, and the  maxi-
+        The maximum length of name for a named subpattern is 32 characters, and
-        mum number of named subpatterns is 10000.
+        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. When you do this, both the pattern  and
-        any subject strings that are matched against it are  treated  as  UTF-8
+        any  subject  strings  that are matched against it are treated as UTF-8
         strings instead of just strings of bytes.
-        If  you compile PCRE with UTF-8 support, but do not use it at run time,
+        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
+        the  library will be a bit bigger, but the additional run time overhead
-        is  limited  to testing the PCRE_UTF8 flag in several places, so should
+        is limited to testing the PCRE_UTF8 flag occasionally, so should not be
-        not be very large.
+        very big.
         If PCRE is built with Unicode character property support (which implies
-        UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-
+        UTF-8 support), the escape sequences \p{..}, \P{..}, and  \X  are  sup-
         ported.  The available properties that can be tested are limited to the
-        general  category  properties such as Lu for an upper case letter or Nd
+        general category properties such as Lu for an upper case letter  or  Nd
-        for a decimal number, the Unicode script names such as Arabic  or  Han,
+        for  a  decimal number, the Unicode script names such as Arabic or Han,
-        and  the  derived  properties  Any  and L&. A full list is given in the
+        and the derived properties Any and L&. A full  list  is  given  in  the
         pcrepattern documentation. Only the short names for properties are sup-
-        ported.  For example, \p{L} matches a letter. Its Perl synonym, \p{Let-
+        ported. For example, \p{L} matches a letter. Its Perl synonym,  \p{Let-
-        ter}, is not supported.  Furthermore,  in  Perl,  many  properties  may
+        ter},  is  not  supported.   Furthermore,  in Perl, many properties may
-        optionally  be  prefixed by "Is", for compatibility with Perl 5.6. PCRE
+        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:
-. When you set the PCRE_UTF8 flag, the strings passed as patterns  and
+.  When you set the PCRE_UTF8 flag, the strings passed as patterns and
-        subjects  are  checked for validity on entry to the relevant functions.
+        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
+        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,
+        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)
+        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
+        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
+        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
+        PCRE_NO_UTF8_CHECK is set, the results are undefined. Your program  may
         crash.
-. An unbraced hexadecimal escape sequence (such  as  \xb3)  matches  a
+.  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
+. 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-
+.  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-
+. 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
+.  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
+        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
+.  The  character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly
-        test  characters of any code value, but the characters that PCRE recog-
+        test characters of any code value, but the characters that PCRE  recog-
-        nizes as digits, spaces, or word characters  remain  the  same  set  as
+        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
+        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
+        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
+        sense  of,  say,  "digit",  you must use Unicode property tests such as
         \p{Nd}.
-.  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
+.  Case-insensitive  matching  applies only to characters whose values
-        are  less than 128, unless PCRE is built with Unicode property support.
+        are less than 128, unless PCRE is built with Unicode property  support.
-        Even when Unicode property support is available, PCRE  still  uses  its
+        Even  when  Unicode  property support is available, PCRE still uses its
-        own  character  tables when checking the case of low-valued characters,
+        own character tables when checking the case of  low-valued  characters,
-        so as not to degrade performance.  The Unicode property information  is
+        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 209 
 AUTHOR
+Line 212 
 AUTHOR
         Philip Hazel
         University Computing Service,
-        Cambridge CB2 3QG, England.
+        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 initial and sur-
         name, separated by a dot, at the domain ucs.cam.ac.uk.
- Last updated: 05 June 2006
+ Last updated: 23 November 2006
  Copyright (c) 1997-2006 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 305 
 CODE VALUE OF NEWLINE
+Line 308 
 CODE VALUE OF NEWLINE
           --enable-newline-is-crlf
-        to  the  configure command. Whatever line ending convention is selected
+        to the configure command. There is a fourth option, specified by
-        when PCRE is built can be overridden when  the  library  functions  are
-        called.  At  build time it is conventional to use the standard for your
+          --enable-newline-is-any
-        operating system.
+        which causes PCRE to recognize any Unicode newline sequence.
+        Whatever  line  ending convention is selected when PCRE is built can be
+        overridden when the library functions are called. At build time  it  is
+        conventional to use the standard for your operating system.
  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 326 
 BUILDING SHARED AND STATIC LIBRARIES
+Line 334 
 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 341 
 POSIX MALLOC USAGE
+Line 349 
 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 enormous patterns, so it
-        is  possible  to compile PCRE to use three-byte or four-byte offsets by
+        is possible to compile PCRE to use three-byte or four-byte  offsets  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.
-        If you build PCRE with an increased link size, test 2 (and  test  5  if
+        If  you  build  PCRE with an increased link size, test 2 (and test 5 if
-        you  are using UTF-8) will fail. Part of the output of these tests is a
+        you are using UTF-8) will fail. Part of the output of these tests is  a
-        representation of the compiled pattern, and this changes with the  link
+        representation  of the compiled pattern, and this changes with the link
         size.
  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.  Separate  functions are provided because the usage is
-        very  predictable:  the  block sizes requested are always the same, and
+        very predictable: the block sizes requested are always  the  same,  and
-        the blocks are always freed in reverse order. A calling  program  might
+        the  blocks  are always freed in reverse order. A calling program might
-        be  able  to implement optimized functions that perform better than the
+        be able to implement optimized functions that perform better  than  the
-        standard malloc() and  free()  functions.  PCRE  runs  noticeably  more
+        standard  malloc()  and  free()  functions.  PCRE  runs noticeably more
         slowly when built in this way. This option affects only the pcre_exec()
         function; it is not relevant for the the pcre_dfa_exec() function.
  LIMITING PCRE RESOURCE USAGE
-        Internally, PCRE has a function called match(), which it calls  repeat-
+        Internally,  PCRE has a function called match(), which it calls repeat-
-        edly   (sometimes   recursively)  when  matching  a  pattern  with  the
+        edly  (sometimes  recursively)  when  matching  a  pattern   with   the
-        pcre_exec() function. By controlling the maximum number of  times  this
+        pcre_exec()  function.  By controlling the maximum number of times this
-        function  may be called during a single matching operation, a limit can
+        function may be called during a single matching operation, a limit  can
-        be placed on the resources used by a single call  to  pcre_exec().  The
+        be  placed  on  the resources used by a single call to pcre_exec(). The
-        limit  can be changed at run time, as described in the pcreapi documen-
+        limit can be changed at run time, as described in the pcreapi  documen-
-        tation. The default is 10 million, but this can be changed by adding  a
+        tation.  The default is 10 million, but this can be changed by adding a
         setting such as
           --with-match-limit=500000
-        to   the   configure  command.  This  setting  has  no  effect  on  the
+        to  the  configure  command.  This  setting  has  no  effect   on   the
         pcre_dfa_exec() matching function.
-        In some environments it is desirable to limit the  depth  of  recursive
+        In  some  environments  it is desirable to limit the depth of recursive
         calls of match() more strictly than the total number of calls, in order
-        to restrict the maximum amount of stack (or heap,  if  --disable-stack-
+        to  restrict  the maximum amount of stack (or heap, if --disable-stack-
         for-recursion is specified) that is used. A second limit controls this;
-        it defaults to the value that  is  set  for  --with-match-limit,  which
+        it  defaults  to  the  value  that is set for --with-match-limit, which
-        imposes  no  additional constraints. However, you can set a lower limit
+        imposes no additional constraints. However, you can set a  lower  limit
         by adding, for example,
           --with-match-limit-recursion=10000
-        to the configure command. This value can  also  be  overridden  at  run
+        to  the  configure  command.  This  value can also be overridden at run
         time.
  USING EBCDIC CODE
-        PCRE  assumes  by  default that it will run in an environment where the
+        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).
+        character  code  is  ASCII  (or Unicode, which is a superset of ASCII).
-        PCRE  can,  however,  be  compiled  to  run in an EBCDIC environment by
+        PCRE can, however, be compiled to  run  in  an  EBCDIC  environment  by
         adding
           --enable-ebcdic
         to the configure command.
- Last updated: 06 June 2006
+ SEE ALSO
+        pcreapi(3), pcre_config(3).
+ Last updated: 30 November 2006
  Copyright (c) 1997-2006 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 466 
 PCRE MATCHING ALGORITHMS
+Line 479 
 PCRE MATCHING ALGORITHMS
           <something> <something else> <something further>
         there are three possible answers. The standard algorithm finds only one
-        of them, whereas the DFA algorithm finds all three.
+        of them, whereas the alternative algorithm finds all three.
  REGULAR EXPRESSIONS AS TREES
-Line 507 
 THE STANDARD MATCHING ALGORITHM
+Line 520 
 THE STANDARD MATCHING ALGORITHM
         This provides support for capturing parentheses and back references.
- THE DFA MATCHING ALGORITHM
+ THE ALTERNATIVE MATCHING ALGORITHM
-        DFA stands for "deterministic finite automaton", but you do not need to
+        This algorithm conducts a breadth-first search of  the  tree.  Starting
-        understand the origins of that name. This algorithm conducts a breadth-
+        from  the  first  matching  point  in the subject, it scans the subject
-        first search of the tree. Starting from the first matching point in the
+        string from left to right, once, character by character, and as it does
-        subject,  it scans the subject string from left to right, once, charac-
+        this,  it remembers all the paths through the tree that represent valid
-        ter by character, and as it does  this,  it  remembers  all  the  paths
+        matches. In Friedl's terminology, this is a kind  of  "DFA  algorithm",
-        through the tree that represent valid matches.
+        though  it is not implemented as a traditional finite state machine (it
+        keeps multiple states active simultaneously).
-        The  scan  continues until either the end of the subject is reached, or
-        there are no more unterminated paths. At this point,  terminated  paths
+        The scan continues until either the end of the subject is  reached,  or
-        represent  the different matching possibilities (if there are none, the
+        there  are  no more unterminated paths. At this point, terminated paths
-        match has failed).  Thus, if there is more  than  one  possible  match,
+        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.  In PCRE, there is an option to stop the algorithm after the first
         match (which is necessarily the shortest) has been found.
         Note that all the matches that are found start at the same point in the
-Line 529 
 THE DFA MATCHING ALGORITHM
+Line 543 
 THE DFA MATCHING ALGORITHM
           cat(er(pillar)?)
-        is matched against the string "the caterpillar catchment",  the  result
+        is  matched  against the string "the caterpillar catchment", the result
-        will  be the three strings "cat", "cater", and "caterpillar" that start
+        will be the three strings "cat", "cater", and "caterpillar" that  start
         at the fourth character of the subject. The algorithm does not automat-
         ically move on to find matches that start at later positions.
         There are a number of features of PCRE regular expressions that are not
-        supported by the DFA matching algorithm. They are as follows:
+        supported by the alternative matching algorithm. They are as follows:
-. Because the algorithm finds all  possible  matches,  the  greedy  or
+.  Because  the  algorithm  finds  all possible matches, the greedy or
-        ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
+        ungreedy nature of repetition quantifiers is not relevant.  Greedy  and
-        ungreedy quantifiers are treated in exactly the same way.
+        ungreedy quantifiers are treated in exactly the same way. However, pos-
+        sessive quantifiers can make a difference when what follows could  also
+        match what is quantified, for example in a pattern like this:
+          ^a++\w!
+        This  pattern matches "aaab!" but not "aaa!", which would be matched by
+        a non-possessive quantifier. Similarly, if an atomic group is  present,
+        it  is matched as if it were a standalone pattern at the current point,
+        and the longest match is then "locked in" for the rest of  the  overall
+        pattern.
 . When dealing with multiple paths through the tree simultaneously, it
-        is  not  straightforward  to  keep track of captured substrings for the
+        is not straightforward to keep track of  captured  substrings  for  the
-        different matching possibilities, and  PCRE's  implementation  of  this
+        different  matching  possibilities,  and  PCRE's implementation of this
         algorithm does not attempt to do this. This means that no captured sub-
         strings are available.
-. Because no substrings are captured, back references within the  pat-
+.  Because no substrings are captured, back references within the pat-
         tern are not supported, and cause errors if encountered.
-.  For  the same reason, conditional expressions that use a backrefer-
+. For the same reason, conditional expressions that use  a  backrefer-
-        ence as the condition are not supported.
+        ence  as  the  condition or test for a specific group recursion are not
+        supported.
 . 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
-        single byte, even in UTF-8 mode, is not supported because the DFA algo-
+        single byte, even in UTF-8 mode, is not supported because the  alterna-
-        rithm moves through the subject string one character at a time, for all
+        tive  algorithm  moves  through  the  subject string one character at a
-        active paths through the tree.
+        time, for all active paths through the tree.
- ADVANTAGES OF THE DFA ALGORITHM
+ ADVANTAGES OF THE ALTERNATIVE ALGORITHM
-        Using the DFA matching algorithm provides the following advantages:
+        Using the alternative matching algorithm provides the following  advan-
+        tages:
 . All possible matches (at a single point in the subject) are automat-
-        ically  found,  and  in particular, the longest match is found. To find
+        ically found, and in particular, the longest match is  found.  To  find
         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
+. There is much better support for partial matching. The  restrictions
-        on the content of the pattern that apply when using the standard  algo-
+        on  the content of the pattern that apply when using the standard algo-
-        rithm  for partial matching do not apply to the DFA algorithm. For non-
+        rithm for partial matching do not apply to the  alternative  algorithm.
-        anchored patterns, the starting position of a partial match  is  avail-
+        For  non-anchored patterns, the starting position of a partial match is
-        able.
+        available.
-.  Because  the  DFA algorithm scans the subject string just once, and
+. Because the alternative algorithm  scans  the  subject  string  just
-        never needs to backtrack, it is possible  to  pass  very  long  subject
+        once,  and  never  needs to backtrack, it is possible to pass very long
-        strings  to  the matching function in several pieces, checking for par-
+        subject strings to the matching function in  several  pieces,  checking
-        tial matching each time.
+        for partial matching each time.
- DISADVANTAGES OF THE DFA ALGORITHM
+ DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
-        The DFA algorithm suffers from a number of disadvantages:
+        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.
-. The "atomic group" feature of PCRE regular expressions is supported,
+. Although atomic groups are supported, their use does not provide the
-        but  does not provide the advantage that it does for the standard algo-
+        performance advantage that it does for the standard algorithm.
-        rithm.
- Last updated: 06 June 2006
+ Last updated: 24 November 2006
  Copyright (c) 1997-2006 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 692 
 PCRE NATIVE API
+Line 717 
 PCRE NATIVE API
  PCRE API OVERVIEW
         PCRE has its own native API, which is described in this document. There
-        is also a set of wrapper functions that correspond to the POSIX regular
+        are also some wrapper functions that correspond to  the  POSIX  regular
         expression  API.  These  are  described in the pcreposix documentation.
         Both of these APIs define a set of C function calls. A C++  wrapper  is
         distributed with PCRE. It is documented in the pcrecpp page.
-Line 715 
 PCRE API OVERVIEW
+Line 740 
 PCRE API OVERVIEW
         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
         ble,  is  also provided. This uses a different algorithm for the match-
         ing. The alternative algorithm finds all possible matches (at  a  given
-        point in the subject). However, this algorithm does not return captured
+        point  in  the subject), and scans the subject just once. However, this
-        substrings. A description of the  two  matching  algorithms  and  their
+        algorithm does not return captured substrings. A description of the two
-        advantages  and  disadvantages  is given in the pcrematching documenta-
+        matching  algorithms and their advantages and disadvantages is given in
-        tion.
+        the pcrematching documentation.
         In addition to the main compiling and  matching  functions,  there  are
         convenience functions for extracting captured substrings from a subject
-Line 779 
 PCRE API OVERVIEW
+Line 804 
 PCRE API OVERVIEW
  NEWLINES
-        PCRE supports three different conventions for indicating line breaks in
-        strings: a single CR character, a single LF character, or the two-char-
+        PCRE  supports four different conventions for indicating line breaks in
-        acter  sequence  CRLF.  All  three  are used as "standard" by different
+        strings: a single CR (carriage return) character, a  single  LF  (line-
-        operating systems.  When PCRE is built, a default can be specified. The
+        feed)  character,  the two-character sequence CRLF, or any Unicode new-
-        default  default  is  LF, which is the Unix standard. When PCRE is run,
+        line sequence.  The Unicode newline sequences are the three  just  men-
-        the default can be overridden, either when a pattern  is  compiled,  or
+        tioned, plus the single characters VT (vertical tab, U+000B), FF (form-
-        when it is matched.
+        feed, U+000C), NEL (next line, U+0085), LS  (line  separator,  U+2028),
+        and PS (paragraph separator, U+2029).
+        Each  of  the first three conventions is used by at least one operating
+        system as its standard newline sequence. When PCRE is built, a  default
+        can  be  specified.  The default default is LF, which is the Unix stan-
+        dard. When PCRE is run, the default can be overridden,  either  when  a
+        pattern is compiled, or when it is matched.
         In the PCRE documentation the word "newline" is used to mean "the char-
-        acter or pair of characters that indicate a line break".
+        acter or pair of characters that indicate a line break". The choice  of
+        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-
+        ment for a non-anchored pattern. The choice of newline convention  does
+        not affect the interpretation of the \n or \r escape sequences.
  MULTITHREADING
-        The PCRE functions can be used in  multi-threading  applications,  with
+        The  PCRE  functions  can be used in multi-threading applications, with
         the  proviso  that  the  memory  management  functions  pointed  to  by
         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
         callout function pointed to by pcre_callout, are shared by all threads.
-        The compiled form of a regular expression is not altered during  match-
+        The  compiled form of a regular expression is not altered during match-
         ing, so the same compiled pattern can safely be used by several threads
         at once.
-Line 806 
 MULTITHREADING
+Line 843 
 MULTITHREADING
  SAVING PRECOMPILED PATTERNS FOR LATER USE
         The compiled form of a regular expression can be saved and re-used at a
-        later  time,  possibly by a different program, and even on a host other
+        later time, possibly by a different program, and even on a  host  other
-        than the one on which  it  was  compiled.  Details  are  given  in  the
+        than  the  one  on  which  it  was  compiled.  Details are given in the
         pcreprecompile documentation.
-Line 815 
 CHECKING BUILD-TIME OPTIONS
+Line 852 
 CHECKING BUILD-TIME OPTIONS
         int pcre_config(int what, void *where);
-        The  function pcre_config() makes it possible for a PCRE client to dis-
+        The function pcre_config() makes it possible for a PCRE client to  dis-
         cover which optional features have been compiled into the PCRE library.
-        The  pcrebuild documentation has more details about these optional fea-
+        The pcrebuild documentation has more details about these optional  fea-
         tures.
-        The first argument for pcre_config() is an  integer,  specifying  which
+        The  first  argument  for pcre_config() is an integer, specifying which
         information is required; the second argument is a pointer to a variable
-        into which the information is  placed.  The  following  information  is
+        into  which  the  information  is  placed. The following information is
         available:
           PCRE_CONFIG_UTF8
-        The  output is an integer that is set to one if UTF-8 support is avail-
+        The output is an integer that is set to one if UTF-8 support is  avail-
         able; otherwise it is set to zero.
           PCRE_CONFIG_UNICODE_PROPERTIES
-        The output is an integer that is set to  one  if  support  for  Unicode
+        The  output  is  an  integer  that is set to one if support for Unicode
         character properties is available; otherwise it is set to zero.
           PCRE_CONFIG_NEWLINE
-        The  output  is  an integer whose value specifies the default character
+        The output is an integer whose value specifies  the  default  character
-        sequence that is recognized as meaning "newline". The three values that
+        sequence  that is recognized as meaning "newline". The four values that
-        are supported are: 10 for LF, 13 for CR, and 3338 for CRLF. The default
+        are supported are: 10 for LF, 13 for CR, 3338 for CRLF, and -1 for ANY.
-        should normally be the standard sequence for your operating system.
+        The default should normally be the standard sequence for your operating
+        system.
           PCRE_CONFIG_LINK_SIZE
-Line 909 
 COMPILING A PATTERN
+Line 947 
 COMPILING A PATTERN
         fully relocatable, because it may contain a copy of the tableptr  argu-
         ment, which is an address (see below).
-        The options argument contains independent bits that affect the compila-
+        The options argument contains various bit settings that affect the com-
-        tion. It should be zero if  no  options  are  required.  The  available
+        pilation. It should be zero if no options are required.  The  available
         options  are  described  below. Some of them, in particular, those that
         are compatible with Perl, can also be set and  unset  from  within  the
         pattern  (see  the  detailed  description in the pcrepattern documenta-
-Line 1000 
 COMPILING A PATTERN
+Line 1038 
 COMPILING A PATTERN
         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
         by  a (?s) option setting. A negative class such as [^a] always matches
-        newlines, independent of the setting of this option.
+        newline characters, independent of the setting of this option.
           PCRE_DUPNAMES
-Line 1064 
 COMPILING A PATTERN
+Line 1102 
 COMPILING A PATTERN
           PCRE_NEWLINE_CR
           PCRE_NEWLINE_LF
           PCRE_NEWLINE_CRLF
+          PCRE_NEWLINE_ANY
         These  options  override the default newline definition that was chosen
         when PCRE was built. Setting the first or the second specifies  that  a
         newline  is  indicated  by a single character (CR or LF, respectively).
-        Setting both of them specifies that a newline is indicated by the  two-
+        Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
-        character  CRLF sequence. For convenience, PCRE_NEWLINE_CRLF is defined
+        two-character  CRLF  sequence.  Setting PCRE_NEWLINE_ANY specifies that
-        to contain both bits. The only time that a line break is relevant  when
+        any Unicode newline sequence should be recognized. The Unicode  newline
-        compiling a pattern is if PCRE_EXTENDED is set, and an unescaped # out-
+        sequences  are  the three just mentioned, plus the single characters VT
-        side a character class is encountered. This indicates  a  comment  that
+        (vertical tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085),
-        lasts until after the next newline.
+        LS  (line separator, U+2028), and PS (paragraph separator, U+2029). The
+        last two are recognized only in UTF-8 mode.
+        The newline setting in the  options  word  uses  three  bits  that  are
+        treated  as  a  number, giving eight possibilities. Currently only five
+        are used (default plus the four values above). This means that  if  you
+        set  more  than  one  newline option, the combination may or may not be
+        sensible. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is  equiva-
+        lent  to PCRE_NEWLINE_CRLF, but other combinations yield unused numbers
+        and cause an error.
+        The only time that a line break is specially recognized when  compiling
+        a  pattern  is  if  PCRE_EXTENDED  is set, and an unescaped # outside a
+        character class is encountered. This indicates  a  comment  that  lasts
+        until  after the next line break sequence. In other circumstances, line
+        break  sequences  are  treated  as  literal  data,   except   that   in
+        PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters
+        and are therefore ignored.
-        The newline option set at compile time becomes the default that is used
+        The newline option that is set at compile time becomes the default that
-        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
-Line 1119 
 COMPILATION ERROR CODES
+Line 1175 
 COMPILATION ERROR CODES
         The following table lists the error  codes  than  may  be  returned  by
         pcre_compile2(),  along with the error messages that may be returned by
-        both compiling functions.
+        both compiling functions. As PCRE has developed, some error codes  have
+        fallen out of use. To avoid confusion, they have not been re-used.
  no error
  \ at end of pattern
-Line 1131 
 COMPILATION ERROR CODES
+Line 1188 
 COMPILATION ERROR CODES
  invalid escape sequence in character class
  range out of order in character class
  nothing to repeat
- operand of unlimited repeat could match the empty string
+ [this code is not in use]
  internal error: unexpected repeat
  unrecognized character after (?
  POSIX named classes are supported only within a class
-Line 1140 
 COMPILATION ERROR CODES
+Line 1197 
 COMPILATION ERROR CODES
  erroffset passed as NULL
  unknown option bit(s) set
  missing ) after comment
- parentheses nested too deeply
+ [this code is not in use]
  regular expression too large
  failed to get memory
  unmatched parentheses
-Line 1154 
 COMPILATION ERROR CODES
+Line 1211 
 COMPILATION ERROR CODES
  unknown POSIX class name
  POSIX collating elements are not supported
  this version of PCRE is not compiled with PCRE_UTF8 support
- spare error
+ [this code is not in use]
  character value in \x{...} sequence is too large
  invalid condition (?(0)
  \C not allowed in lookbehind assertion
-Line 1163 
 COMPILATION ERROR CODES
+Line 1220 
 COMPILATION ERROR CODES
  closing ) for (?C expected
  recursive call could loop indefinitely
  unrecognized character after (?P
- syntax error after (?P
+ syntax error in subpattern name (missing terminator)
  two named subpatterns have the same name
  invalid UTF-8 string
  support for \P, \p, and \X has not been compiled
-Line 1173 
 COMPILATION ERROR CODES
+Line 1230 
 COMPILATION ERROR CODES
  too many named subpatterns (maximum 10,000)
  repeated subpattern is too long
  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"
  STUDYING A PATTERN
-Line 1331 
 INFORMATION ABOUT A PATTERN
+Line 1394 
 INFORMATION ABOUT A PATTERN
         is still recognized for backwards compatibility.)
         If there is a fixed first byte, for example, from  a  pattern  such  as
-        (cat|cow|coyote). Otherwise, if either
+        (cat|cow|coyote), its value is returned. Otherwise, if either
         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every
         branch starts with "^", or
-Line 1388 
 INFORMATION ABOUT A PATTERN
+Line 1451 
 INFORMATION ABOUT A PATTERN
         PCRE_EXTENDED  is  set,  so  white  space  -  including  newlines  - is
         ignored):
-          (?P<date> (?P<year>(\d\d)?\d\d) -
+          (?<date> (?<year>(\d\d)?\d\d) -
-          (?P<month>\d\d) - (?P<day>\d\d) )
+          (?<month>\d\d) - (?<day>\d\d) )
         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,
-Line 1616 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 1679 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
           PCRE_NEWLINE_CR
           PCRE_NEWLINE_LF
           PCRE_NEWLINE_CRLF
+          PCRE_NEWLINE_ANY
         These options override  the  newline  definition  that  was  chosen  or
         defaulted  when the pattern was compiled. For details, see the descrip-
-        tion pcre_compile() above. During matching, the newline choice  affects
+        tion of pcre_compile()  above.  During  matching,  the  newline  choice
-        the behaviour of the dot, circumflex, and dollar metacharacters.
+        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 or
+        PCRE_NEWLINE_ANY is set, and a match attempt  fails  when  the  current
+        position  is  at a CRLF sequence, the match position is advanced by two
+        characters instead of one, in other words, to after the CRLF.
           PCRE_NOTBOL
         This option specifies that first character of the subject string is not
-        the beginning of a line, so the  circumflex  metacharacter  should  not
+        the  beginning  of  a  line, so the circumflex metacharacter should not
-        match  before it. Setting this without PCRE_MULTILINE (at compile time)
+        match before it. Setting this without PCRE_MULTILINE (at compile  time)
-        causes circumflex never to match. This option affects only  the  behav-
+        causes  circumflex  never to match. This option affects only the behav-
         iour of the circumflex metacharacter. It does not affect \A.
           PCRE_NOTEOL
         This option specifies that the end of the subject string is not the end
-        of a line, so the dollar metacharacter should not match it nor  (except
+        of  a line, so the dollar metacharacter should not match it nor (except
-        in  multiline mode) a newline immediately before it. Setting this with-
+        in multiline mode) a newline immediately before it. Setting this  with-
         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
-        option  affects only the behaviour of the dollar metacharacter. It does
+        option affects only the behaviour of the dollar metacharacter. It  does
         not affect \Z or \z.
           PCRE_NOTEMPTY
         An empty string is not considered to be a valid match if this option is
-        set.  If  there are alternatives in the pattern, they are tried. If all
+        set. If there are alternatives in the pattern, they are tried.  If  all
-        the alternatives match the empty string, the entire  match  fails.  For
+        the  alternatives  match  the empty string, the entire match fails. For
         example, if the pattern
           a?b?
-        is  applied  to  a string not beginning with "a" or "b", it matches the
+        is applied to a string not beginning with "a" or "b",  it  matches  the
-        empty string at the start of the subject. With PCRE_NOTEMPTY set,  this
+        empty  string at the start of the subject. With PCRE_NOTEMPTY set, this
         match is not valid, so PCRE searches further into the string for occur-
         rences of "a" or "b".
         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-
-        cial  case  of  a  pattern match of the empty string within its split()
+        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
+        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 offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then
-        if  that  fails by advancing the starting offset (see below) and trying
+        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
         this in the pcredemo.c sample program.
           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
+        UTF-8  string is automatically checked when pcre_exec() is subsequently
-        called.   The  value  of  startoffset is also checked to ensure that it
+        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. If an invalid UTF-8 sequence
         of bytes is found, pcre_exec() returns the error PCRE_ERROR_BADUTF8. If
-        startoffset contains an  invalid  value,  PCRE_ERROR_BADUTF8_OFFSET  is
+        startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is
         returned.
-        If  you  already  know that your subject is valid, and you want to skip
+        If you already know that your subject is valid, and you  want  to  skip
-        these   checks   for   performance   reasons,   you   can    set    the
+        these    checks    for   performance   reasons,   you   can   set   the
-        PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to
+        PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to
-        do this for the second and subsequent calls to pcre_exec() if  you  are
+        do  this  for the second and subsequent calls to pcre_exec() if you are
-        making  repeated  calls  to  find  all  the matches in a single subject
+        making repeated calls to find all  the  matches  in  a  single  subject
-        string. However, you should be  sure  that  the  value  of  startoffset
+        string.  However,  you  should  be  sure  that the value of startoffset
-        points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is
+        points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is
-        set, the effect of passing an invalid UTF-8 string as a subject,  or  a
+        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-
+        value of startoffset that does not point to the start of a UTF-8  char-
         acter, is undefined. Your program may crash.
           PCRE_PARTIAL
-        This option turns on the  partial  matching  feature.  If  the  subject
+        This  option  turns  on  the  partial  matching feature. If the subject
-        string  fails to match the pattern, but at some point during the match-
+        string fails to match the pattern, but at some point during the  match-
-        ing process the end of the subject was reached (that  is,  the  subject
+        ing  process  the  end of the subject was reached (that is, the subject
-        partially  matches  the  pattern and the failure to match occurred only
+        partially matches the pattern and the failure to  match  occurred  only
-        because there were not enough subject characters), pcre_exec()  returns
+        because  there were not enough subject characters), pcre_exec() returns
-        PCRE_ERROR_PARTIAL  instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is
+        PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is
-        used, there are restrictions on what may appear in the  pattern.  These
+        used,  there  are restrictions on what may appear in the pattern. These
         are discussed 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
+        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  length, and a starting byte offset in startoffset. In UTF-8
-        mode,  the  byte  offset  must point to the start of a UTF-8 character.
+        mode, the byte offset must point to the start  of  a  UTF-8  character.
-        Unlike the pattern string, the subject may contain binary  zero  bytes.
+        Unlike  the  pattern string, the subject may contain binary zero bytes.
-        When  the starting offset is zero, the search for a match starts at the
+        When the starting offset is zero, the search for a match starts 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
+        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-
+        in the same subject by calling pcre_exec() again after a previous  suc-
-        cess.  Setting startoffset differs from just passing over  a  shortened
+        cess.   Setting  startoffset differs from just passing over a shortened
-        string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins
+        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 integer
-        offsets  whose  address is passed in ovector. The number of elements in
+        offsets whose address is passed in ovector. The number of  elements  in
-        the vector is passed in ovecsize, which must be a non-negative  number.
+        the  vector is passed in ovecsize, which must be a non-negative number.
         Note: 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 length 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-
-        string, and the second is set to the  offset  of  the  first  character
+        string,  and  the  second  is  set to the offset of the first character
-        after  the  end  of  a  substring. The first pair, ovector[0] and ovec-
+        after the end of a substring. The  first  pair,  ovector[0]  and  ovec-
-        tor[1], identify the portion of  the  subject  string  matched  by  the
+        tor[1],  identify  the  portion  of  the  subject string matched by the
-        entire  pattern.  The next pair is used for the first capturing subpat-
+        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
         highest numbered pair that has been set. For example, if two substrings
-        have been captured, the returned value is 3. If there are no  capturing
+        have  been captured, the returned value is 3. If there are no capturing
-        subpatterns,  the return value from a successful match is 1, indicating
+        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,
+        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. In particular, if the substring  off-
         sets are not of interest, pcre_exec() may be called with ovector passed
-        as  NULL  and  ovecsize  as zero. However, if the pattern contains back
+        as NULL and ovecsize as zero. However, if  the  pattern  contains  back
-        references and the ovector is not big enough to  remember  the  related
+        references  and  the  ovector is not big enough to remember the related
-        substrings,  PCRE has to get additional memory for use during matching.
+        substrings, PCRE has to get additional memory for use during  matching.
         Thus it is usually advisable to supply an ovector.
-        The pcre_info() function can be used to find  out  how  many  capturing
+        The  pcre_info()  function  can  be used to find out how many capturing
-        subpatterns  there  are  in  a  compiled pattern. The smallest size for
+        subpatterns there are in a compiled  pattern.  The  smallest  size  for
-        ovector that will allow for n captured substrings, in addition  to  the
+        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.
-        It  is  possible for capturing subpattern number n+1 to match some part
+        It is possible for capturing subpattern number n+1 to match  some  part
         of the subject when subpattern n has not been used at all. For example,
-        if  the  string  "abc"  is  matched against the pattern (a|(z))(bc) the
+        if the string "abc" is matched  against  the  pattern  (a|(z))(bc)  the
         return from the function is 4, and subpatterns 1 and 3 are matched, but
- is  not.  When  this happens, both values in the offset pairs corre-
+is not. When this happens, both values in  the  offset  pairs  corre-
         sponding to unused subpatterns are set to -1.
-        Offset values that correspond to unused subpatterns at the end  of  the
+        Offset  values  that correspond to unused subpatterns at the end of the
-        expression  are  also  set  to  -1. For example, if the string "abc" is
+        expression are also set to -1. For example,  if  the  string  "abc"  is
-        matched against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are  not
+        matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not
-        matched.  The  return  from the function is 2, because the highest used
+        matched. The return from the function is 2, because  the  highest  used
         capturing subpattern number is 1. However, you can refer to the offsets
-        for  the  second  and third capturing subpatterns if you wish (assuming
+        for the second and third capturing subpatterns if  you  wish  (assuming
         the vector is large enough, of course).
-        Some convenience functions are provided  for  extracting  the  captured
+        Some  convenience  functions  are  provided for extracting the captured
         substrings as separate strings. These are described below.
     Error return values from pcre_exec()
-        If  pcre_exec()  fails, it returns a negative number. The following are
+        If pcre_exec() fails, it returns a negative number. The  following  are
         defined in the header file:
           PCRE_ERROR_NOMATCH        (-1)
-Line 1809 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 1878 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
           PCRE_ERROR_NULL           (-2)
-        Either code or subject was passed as NULL,  or  ovector  was  NULL  and
+        Either  code  or  subject  was  passed as NULL, or ovector was NULL and
         ovecsize was not zero.
           PCRE_ERROR_BADOPTION      (-3)
-Line 1818 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
+Line 1887 
 MATCHING A PATTERN: THE TRADITIONAL FUNC
           PCRE_ERROR_BADMAGIC       (-4)
-        PCRE  stores a 4-byte "magic number" at the start of the compiled code,
+        PCRE stores a 4-byte "magic number" at the start of the compiled  code,
         to catch the case when it is passed a junk pointer and to detect when a
         pattern that was compiled in an environment of one endianness is run in
-        an environment with the other endianness. This is the error  that  PCRE
+        an  environment  with the other endianness. This is the error that PCRE
         gives when the magic number is not present.
-          PCRE_ERROR_UNKNOWN_NODE   (-5)
+          PCRE_ERROR_UNKNOWN_OPCODE (-5)
         While running the pattern match, an unknown item was encountered in the
-        compiled pattern. This error could be caused by a bug  in  PCRE  or  by
+        compiled  pattern.  This  error  could be caused by a bug in PCRE or by
         overwriting of the compiled pattern.
           PCRE_ERROR_NOMEMORY       (-6)
-        If  a  pattern contains back references, but the ovector that is passed
+        If a pattern contains back references, but the ovector that  is  passed
         to pcre_exec() is not big enough to remember the referenced substrings,
-        PCRE  gets  a  block of memory at the start of matching to use for this
+        PCRE gets a block of memory at the start of matching to  use  for  this
-        purpose. If the call via pcre_malloc() fails, this error is given.  The
+        purpose.  If the call via pcre_malloc() fails, this error is given. The
         memory is automatically freed at the end of matching.
           PCRE_ERROR_NOSUBSTRING    (-7)
-        This  error is used by the pcre_copy_substring(), pcre_get_substring(),
+        This error is used by the pcre_copy_substring(),  pcre_get_substring(),
         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
         returned by pcre_exec().
           PCRE_ERROR_MATCHLIMIT     (-8)
-        The  backtracking  limit,  as  specified  by the match_limit field in a
+        The backtracking limit, as specified by  the  match_limit  field  in  a
-        pcre_extra structure (or defaulted) was reached.  See  the  description
+        pcre_extra  structure  (or  defaulted) was reached. See the description
         above.
-          PCRE_ERROR_RECURSIONLIMIT (-21)
-        The internal recursion limit, as specified by the match_limit_recursion
-        field in a pcre_extra structure (or defaulted)  was  reached.  See  the
-        description above.
           PCRE_ERROR_CALLOUT        (-9)
         This error is never generated by pcre_exec() itself. It is provided for
-        use by callout functions that want to yield a distinctive  error  code.
+        use  by  callout functions that want to yield a distinctive error code.
         See the pcrecallout documentation for details.
           PCRE_ERROR_BADUTF8        (-10)
-        A  string  that contains an invalid UTF-8 byte sequence was passed as a
+        A string that contains an invalid UTF-8 byte sequence was passed  as  a
         subject.
           PCRE_ERROR_BADUTF8_OFFSET (-11)
         The UTF-8 byte sequence that was passed as a subject was valid, but the
-        value  of startoffset did not point to the beginning of a UTF-8 charac-
+        value of startoffset did not point to the beginning of a UTF-8  charac-
         ter.
           PCRE_ERROR_PARTIAL        (-12)
-        The subject string did not match, but it did match partially.  See  the
+        The  subject  string did not match, but it did match partially. See the
         pcrepartial documentation for details of partial matching.
           PCRE_ERROR_BADPARTIAL     (-13)
-        The  PCRE_PARTIAL  option  was  used with a compiled pattern containing
+        The PCRE_PARTIAL option was used with  a  compiled  pattern  containing
-        items that are not supported for partial matching. See the  pcrepartial
+        items  that are not supported for partial matching. See the pcrepartial
         documentation for details of 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)
+        The internal recursion limit, as specified by the match_limit_recursion
+        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().
  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
-Line 1907 
 EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
+Line 1990 
 EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
         int pcre_get_substring_list(const char *subject,
              int *ovector, int stringcount, const char ***listptr);
-        Captured  substrings  can  be  accessed  directly  by using the offsets
+        Captured substrings can be  accessed  directly  by  using  the  offsets
-        returned by pcre_exec() in  ovector.  For  convenience,  the  functions
+        returned  by  pcre_exec()  in  ovector.  For convenience, the functions
         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
-        string_list() are provided for extracting captured substrings  as  new,
+        string_list()  are  provided for extracting captured substrings as new,
-        separate,  zero-terminated strings. These functions identify substrings
+        separate, zero-terminated strings. These functions identify  substrings
-        by number. The next section describes functions  for  extracting  named
+        by  number.  The  next section describes functions for extracting named
         substrings.
-        A  substring that contains a binary zero is correctly extracted and has
+        A substring that contains a binary zero is correctly extracted and  has
-        a further zero added on the end, but the result is not, of course, a  C
+        a  further zero added on the end, but the result is not, of course, a C
-        string.   However,  you  can  process such a string by referring to the
+        string.  However, you can process such a string  by  referring  to  the
-        length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
+        length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-
         string().  Unfortunately, the interface to pcre_get_substring_list() is
-        not adequate for handling strings containing binary zeros, because  the
+        not  adequate for handling strings containing binary zeros, because the
         end of the final string is not independently indicated.
-        The  first  three  arguments  are the same for all three of these func-
+        The first three arguments are the same for all  three  of  these  func-
-        tions: subject is the subject string that has  just  been  successfully
+        tions:  subject  is  the subject string that has just been successfully
         matched, ovector is a pointer to the vector of integer offsets that was
         passed to pcre_exec(), and stringcount is the number of substrings that
-        were  captured  by  the match, including the substring that matched the
+        were captured by the match, including the substring  that  matched  the
         entire regular expression. This is the value returned by pcre_exec() if
-        it  is greater than zero. If pcre_exec() returned zero, indicating that
+        it is greater than zero. If pcre_exec() returned zero, indicating  that
-        it ran out of space in ovector, the value passed as stringcount  should
+        it  ran out of space in ovector, the value passed as stringcount should
         be the number of elements in the vector divided by three.
-        The  functions pcre_copy_substring() and pcre_get_substring() extract a
+        The functions pcre_copy_substring() and pcre_get_substring() extract  a
-        single substring, whose number is given as  stringnumber.  A  value  of
+        single  substring,  whose  number  is given as stringnumber. A value of
-        zero  extracts  the  substring that matched the entire pattern, whereas
+        zero extracts the substring that matched the  entire  pattern,  whereas
-        higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
+        higher  values  extract  the  captured  substrings.  For pcre_copy_sub-
-        string(),  the  string  is  placed  in buffer, whose length is given by
+        string(), the string is placed in buffer,  whose  length  is  given  by
-        buffersize, while for pcre_get_substring() a new  block  of  memory  is
+        buffersize,  while  for  pcre_get_substring()  a new block of memory is
-        obtained  via  pcre_malloc,  and its address is returned via stringptr.
+        obtained via pcre_malloc, and its address is  returned  via  stringptr.
-        The yield of the function is the length of the  string,  not  including
+        The  yield  of  the function is the length of the string, not including
-        the terminating zero, or one of
+        the terminating zero, or one of these error codes:
           PCRE_ERROR_NOMEMORY       (-6)
-        The  buffer  was too small for pcre_copy_substring(), or the attempt to
+        The buffer was too small for pcre_copy_substring(), or the  attempt  to
         get memory failed for pcre_get_substring().
           PCRE_ERROR_NOSUBSTRING    (-7)
         There is no substring whose number is stringnumber.
-        The pcre_get_substring_list()  function  extracts  all  available  sub-
+        The  pcre_get_substring_list()  function  extracts  all  available sub-
-        strings  and  builds  a list of pointers to them. All this is done in a
+        strings and builds a list of pointers to them. All this is  done  in  a
         single block of memory that is obtained via pcre_malloc. The address of
-        the  memory  block  is returned via listptr, which is also the start of
+        the memory block is returned via listptr, which is also  the  start  of
-        the list of string pointers. The end of the list is marked  by  a  NULL
+        the  list  of  string pointers. The end of the list is marked by a NULL
-        pointer. The yield of the function is zero if all went well, or
+        pointer. The yield of the function is zero if all  went  well,  or  the
+        error code
           PCRE_ERROR_NOMEMORY       (-6)
-Line 1999 
 EXTRACTING CAPTURED SUBSTRINGS BY NAME
+Line 2083 
 EXTRACTING CAPTURED SUBSTRINGS BY NAME
         To extract a substring by name, you first have to find associated  num-
         ber.  For example, for this pattern
-          (a+)b(?P<xxx>\d+)...
+          (a+)b(?<xxx>\d+)...
         the number of the subpattern called "xxx" is 2. If the name is known to
         be unique (PCRE_DUPNAMES was not set), you can find the number from the
-Line 2050 
 DUPLICATE SUBPATTERN NAMES
+Line 2134 
 DUPLICATE SUBPATTERN NAMES
         third  and  fourth  are  pointers to variables which are updated by the
         function. After it has run, they point to the first and last entries in
         the  name-to-number  table  for  the  given  name.  The function itself
-        returns the length of each entry, or  PCRE_ERROR_NOSUBSTRING  if  there
+        returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
-        are  none.  The  format  of the table is described above in the section
+        there  are none. The format of the table is described above in the sec-
-        entitled Information about a pattern. Given all  the  relevant  entries
+        tion entitled Information about a  pattern.   Given  all  the  relevant
-        for the name, you can extract each of their numbers, and hence the cap-
+        entries  for the name, you can extract each of their numbers, and hence
-        tured data, if any.
+        the captured data, if any.
  FINDING ALL POSSIBLE MATCHES
-Line 2083 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
+Line 2167 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
              int *workspace, int wscount);
         The  function  pcre_dfa_exec()  is  called  to  match  a subject string
-        against a compiled pattern, using a "DFA" matching algorithm. This  has
+        against a compiled pattern, using a matching algorithm that  scans  the
-        different  characteristics to the normal algorithm, and is not compati-
+        subject  string  just  once, and does not backtrack. This has different
-        ble with Perl. Some of the features of PCRE patterns are not supported.
+        characteristics to the normal algorithm, and  is  not  compatible  with
-        Nevertheless, there are times when this kind of matching can be useful.
+        Perl.  Some  of the features of PCRE patterns are not supported. Never-
-        For a discussion of the two matching algorithms, see  the  pcrematching
+        theless, there are times when this kind of matching can be useful.  For
-        documentation.
+        a discussion of the two matching algorithms, see the pcrematching docu-
+        mentation.
-        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 2121 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
+Line 2206 
 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_NO_UTF8_CHECK,
         PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last
         three of these are the same as for pcre_exec(), so their description is
         not repeated here.
           PCRE_PARTIAL
-        This has the same general effect as it does for  pcre_exec(),  but  the
+        This  has  the  same general effect as it does for pcre_exec(), but the
-        details   are   slightly   different.  When  PCRE_PARTIAL  is  set  for
+        details  are  slightly  different.  When  PCRE_PARTIAL   is   set   for
-        pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is  converted  into
+        pcre_dfa_exec(),  the  return code PCRE_ERROR_NOMATCH is converted into
-        PCRE_ERROR_PARTIAL  if  the  end  of the subject is reached, there have
+        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 pos-
-        sibility.  The portion of the string that provided the partial match is
+        sibility. The portion of the string that provided the partial match  is
         set as the first matching string.
           PCRE_DFA_SHORTEST
-        Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to
+        Setting  the  PCRE_DFA_SHORTEST option causes the matching algorithm to
-        stop  as  soon  as  it  has found one match. Because of the way the DFA
+        stop as soon as it has found one match. Because of the way the alterna-
-        algorithm works, this is necessarily the shortest possible match at the
+        tive  algorithm  works, this is necessarily the shortest possible match
-        first possible matching point in the subject string.
+        at the first possible matching point in the subject string.
           PCRE_DFA_RESTART
-        When  pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option, and
+        When pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option,  and
-        returns a partial match, it is possible to call it  again,  with  addi-
+        returns  a  partial  match, it is possible to call it again, with addi-
-        tional  subject  characters,  and have it continue with the same match.
+        tional subject characters, and have it continue with  the  same  match.
-        The PCRE_DFA_RESTART option requests this action; when it is  set,  the
+        The  PCRE_DFA_RESTART  option requests this action; when it is set, the
-        workspace  and wscount options must reference the same vector as before
+        workspace and wscount options must reference the same vector as  before
-        because data about the match so far is left in  them  after  a  partial
+        because  data  about  the  match so far is left in them after a partial
-        match.  There  is  more  discussion of this facility in the pcrepartial
+        match. There is more discussion of this  facility  in  the  pcrepartial
         documentation.
     Successful returns from pcre_dfa_exec()
-        When pcre_dfa_exec() succeeds, it may have matched more than  one  sub-
+        When  pcre_dfa_exec()  succeeds, it may have matched more than one sub-
         string in the subject. Note, however, that all the matches from one run
-        of the function start at the same point in  the  subject.  The  shorter
+        of  the  function  start  at the same point in the subject. The shorter
-        matches  are all initial substrings of the longer matches. For example,
+        matches are all initial substrings of the longer matches. For  example,
         if the pattern
           <.*>
-Line 2176 
 MATCHING A PATTERN: THE ALTERNATIVE FUNC
+Line 2261 
 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. All
+        the offset to the start, and the second is the offset to  the  end.  In
-        the strings have the same start offset. (Space could have been saved by
+        fact,  all  the  strings  have the same start offset. (Space could have
-        giving  this only once, but it was decided to retain some compatibility
+        been saved by giving this only once, but it was decided to retain  some
-        with the way pcre_exec() returns data, even though the meaning  of  the
+        compatibility  with  the  way pcre_exec() returns data, even though the
-        strings is different.)
+        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 in
+        This return is given if pcre_dfa_exec()  encounters  a  condition  item
-        a pattern that uses a back reference for the  condition.  This  is  not
+        that  uses  a back reference for the condition, or a test for recursion
-        supported.
+        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.
- Last updated: 08 June 2006
+ SEE ALSO
+        pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-
+        tial(3),  pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
+ Last updated: 30 November 2006
  Copyright (c) 1997-2006 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 2401 
 NAME
+Line 2492 
 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  with
+        handle regular expressions. The differences described here  are  mainly
-        respect to Perl 5.8.
+        with  respect  to  Perl 5.8, though PCRE version 7.0 contains some fea-
+        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&.
 . 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 2449 
 DIFFERENCES BETWEEN PCRE AND PERL
+Line 2541 
 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 (?p{code})
+. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
-        constructions.  However,  there is support for recursive patterns using
+        constructions. However, there is support for recursive  patterns.  This
-        the non-Perl items (?R),  (?number),  and  (?P>name).  Also,  the  PCRE
+        is  not available in Perl 5.8, but will be 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.
-. There are some differences that are concerned with the  settings  of
+.  Subpatterns  that  are  called  recursively or as "subroutines" are
-        captured  strings  when  part  of  a  pattern is repeated. For example,
+        always treated as atomic groups in  PCRE.  This  is  like  Python,  but
-        matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2
+        unlike Perl.
+.  There are some differences that are concerned with the settings of
+        captured strings when part of  a  pattern  is  repeated.  For  example,
+        matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2
         unset, but in PCRE it is set to "b".
 . PCRE provides some extensions to the Perl regular expression facil-
-        ities:
+        ities.   Perl  5.10  will  include new features that are not in earlier
+        versions, 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 must  match  fixed  length  strings,
+        (a)  Although  lookbehind  assertions  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
         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, and PCRE_NO_AUTO_CAP-
         TURE options for pcre_exec() have no Perl equivalents.
-        (g)  The (?R), (?number), and (?P>name) constructs allows for recursive
+        (g) The callout facility is PCRE-specific.
-        pattern matching (Perl can do  this  using  the  (?p{code})  construct,
-        which PCRE cannot support.)
-        (h)  PCRE supports named capturing substrings, using the Python syntax.
-        (i) PCRE supports the possessive quantifier  "++"  syntax,  taken  from
-        Sun's Java package.
-        (j) The (R) condition, for testing recursion, is a PCRE extension.
-        (k) The callout facility is PCRE-specific.
-        (l) The partial matching facility is PCRE-specific.
+        (h) The partial matching facility is PCRE-specific.
-        (m) Patterns compiled by PCRE can be saved and re-used at a later time,
+        (i) Patterns compiled by PCRE can be saved and re-used at a later time,
         even on different hosts that have the other endianness.
-        (n) The alternative matching function (pcre_dfa_exec())  matches  in  a
+        (j)  The  alternative  matching function (pcre_dfa_exec()) matches in a
         different way and is not Perl-compatible.
- Last updated: 06 June 2006
+ Last updated: 28 November 2006
  Copyright (c) 1997-2006 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 2545 
 PCRE REGULAR EXPRESSION DETAILS
+Line 2632 
 PCRE REGULAR EXPRESSION DETAILS
         function, and how it differs from the normal function, are discussed in
         the pcrematching page.
+ CHARACTERS AND METACHARACTERS
         A regular expression is a pattern that is  matched  against  a  subject
         string  from  left  to right. Most characters stand for themselves in a
         pattern, and match the corresponding characters in the  subject.  As  a
-Line 2569 
 PCRE REGULAR EXPRESSION DETAILS
+Line 2659 
 PCRE REGULAR EXPRESSION DETAILS
         There are two different sets of metacharacters: those that  are  recog-
         nized  anywhere in the pattern except within square brackets, and those
-        that are recognized in square brackets. Outside  square  brackets,  the
+        that are recognized within square brackets.  Outside  square  brackets,
-        metacharacters are as follows:
+        the metacharacters are as follows:
           \      general escape character with several uses
           ^      assert start of string (or line, in multiline mode)
-Line 2692 
 BACKSLASH
+Line 2782 
 BACKSLASH
         Inside a character class, or if the decimal number is  greater  than  9
         and  there have not been that many capturing subpatterns, PCRE re-reads
-        up to three octal digits following the backslash, ane uses them to gen-
+        up to three octal digits following the backslash, and uses them to gen-
         erate  a data character. Any subsequent digits stand for themselves. In
         non-UTF-8 mode, the value of a character specified  in  octal  must  be
         less  than  \400.  In  UTF-8 mode, values up to \777 are permitted. For
-Line 2719 
 BACKSLASH
+Line 2809 
 BACKSLASH
         All the sequences that define a single character value can be used both
         inside and outside character classes. In addition, inside  a  character
         class,  the  sequence \b is interpreted as the backspace character (hex
-), and the sequence \X is interpreted as the character "X". Outside a
+), and the sequences \R and \X are interpreted as the characters  "R"
-        character class, these sequences have different meanings (see below).
+        and  "X", respectively. Outside a character class, these sequences have
+        different meanings (see below).
+    Absolute and relative back references
+        The sequence \g followed by a positive or negative  number,  optionally
+        enclosed  in  braces,  is  an absolute or relative back reference. Back
+        references are discussed later, following the discussion  of  parenthe-
+        sized subpatterns.
     Generic character types
-        The  third  use of backslash is for specifying generic character types.
+        Another use of backslash is for specifying generic character types. The
-        The following are always recognized:
+        following are always recognized:
           \d     any decimal digit
           \D     any character that is not a decimal digit
-Line 2762 
 BACKSLASH
+Line 2860 
 BACKSLASH
         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
+        newline sequence. This is an extension to Perl. In non-UTF-8 mode \R is
+        equivalent to the following:
+          (?>\r\n|\n|\x0b|\f|\r|\x85)
+        This is an example of an "atomic group", details  of  which  are  given
+        below.  This particular group matches either the two-character sequence
+        CR followed by LF, or  one  of  the  single  characters  LF  (linefeed,
+        U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage
+        return, U+000D), or NEL (next line, U+0085). The two-character sequence
+        is treated as a single unit that cannot be split.
+        In  UTF-8  mode, two additional characters whose codepoints are greater
+        than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-
+        rator,  U+2029).   Unicode character property support is not needed for
+        these characters to be recognized.
+        Inside a character class, \R matches the letter "R".
     Unicode character properties
         When PCRE is built with Unicode character property support, three addi-
-Line 2788 
 BACKSLASH
+Line 2908 
 BACKSLASH
         Those that are not part of an identified script are lumped together  as
         "Common". The current list of scripts is:
-        Arabic,  Armenian,  Bengali,  Bopomofo, Braille, Buginese, Buhid, Cana-
+        Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,
-        dian_Aboriginal, Cherokee, Common, Coptic, Cypriot, Cyrillic,  Deseret,
+        Buhid,  Canadian_Aboriginal,  Cherokee,  Common,   Coptic,   Cuneiform,
-        Devanagari,  Ethiopic,  Georgian,  Glagolitic, Gothic, Greek, Gujarati,
+        Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,
-        Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hiragana,  Inherited,  Kannada,
+        Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew,  Hira-
-        Katakana,  Kharoshthi,  Khmer,  Lao, Latin, Limbu, Linear_B, Malayalam,
+        gana,  Inherited,  Kannada,  Katakana,  Kharoshthi,  Khmer, Lao, Latin,
-        Mongolian, Myanmar, New_Tai_Lue, Ogham, Old_Italic, Old_Persian, Oriya,
+        Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,
-        Osmanya,  Runic,  Shavian, Sinhala, Syloti_Nagri, Syriac, Tagalog, Tag-
+        Ogham,  Old_Italic,  Old_Persian, Oriya, Osmanya, Phags_Pa, Phoenician,
-        banwa,  Tai_Le,  Tamil,  Telugu,  Thaana,  Thai,   Tibetan,   Tifinagh,
+        Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,
-        Ugaritic, Yi.
+        Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.
         Each  character has exactly one general category property, specified by
         a two-letter abbreviation. For compatibility with Perl, negation can be
-Line 2889 
 BACKSLASH
+Line 3009 
 BACKSLASH
     Simple assertions
-        The fourth 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
         a  match, without consuming any characters from the subject string. The
         use of subpatterns for more complicated assertions is described  below.
-Line 2897 
 BACKSLASH
+Line 3017 
 BACKSLASH
           \b     matches at a word boundary
           \B     matches when not at a word boundary
-          \A     matches at start of subject
+          \A     matches at the start of the subject
-          \Z     matches at end of subject or before newline at end
+          \Z     matches at the end of the subject
-          \z     matches at end of subject
+                  also matches before a newline at the end of the subject
-          \G     matches at first matching position in subject
+          \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
         has a different meaning, namely the backspace character, inside a char-
-Line 2997 
 FULL STOP (PERIOD, DOT)
+Line 3118 
 FULL STOP (PERIOD, DOT)
         Outside a character class, a dot in the pattern matches any one charac-
         ter in the subject string except (by default) a character  that  signi-
         fies  the  end  of  a line. In UTF-8 mode, the matched character may be
-        more than one byte long. When a line ending  is  defined  as  a  single
+        more than one byte long.
-        character  (CR  or LF), dot never matches that character; when the two-
-        character sequence CRLF is used, dot does not match CR if it is immedi-
-        ately  followed by LF, but otherwise it matches all characters (includ-
-        ing isolated CRs and LFs).
-        The behaviour of dot with regard to newlines can  be  changed.  If  the
-        PCRE_DOTALL  option  is  set,  a dot matches any one character, without
-        exception. If newline is defined as the two-character sequence CRLF, it
-        takes two dots to match it.
-        The  handling of dot is entirely independent of the handling of circum-
+        When a line ending is defined as a single character, dot never  matches
-        flex and dollar, the only relationship being  that  they  both  involve
+        that  character; when the two-character sequence CRLF is used, dot does
+        not match CR if it is immediately followed  by  LF,  but  otherwise  it
+        matches  all characters (including isolated CRs and LFs). When any Uni-
+        code line endings are being recognized, dot does not match CR or LF  or
+        any of the other line ending characters.
+        The  behaviour  of  dot  with regard to newlines can be changed. If the
+        PCRE_DOTALL option is set, a dot matches  any  one  character,  without
+        exception. If the two-character sequence CRLF is present in the subject
+        string, it takes two dots to match it.
+        The handling of dot is entirely independent of the handling of  circum-
+        flex  and  dollar,  the  only relationship being that they both involve
         newlines. Dot has no special meaning in a character class.
  MATCHING A SINGLE BYTE
         Outside a character class, the escape sequence \C matches any one byte,
-        both in and out of UTF-8 mode. Unlike a dot, it always matches  CR  and
+        both  in  and  out  of  UTF-8 mode. Unlike a dot, it always matches any
-        LF.  The feature is provided in Perl in order to match individual bytes
+        line-ending characters. The feature is provided in  Perl  in  order  to
-        in UTF-8 mode.  Because it breaks up UTF-8 characters  into  individual
+        match  individual bytes in UTF-8 mode. Because it breaks up UTF-8 char-
-        bytes,  what remains in the string may be a malformed UTF-8 string. For
+        acters into individual bytes, what remains in the string may be a  mal-
-        this reason, the \C escape sequence is best avoided.
+        formed  UTF-8  string.  For this reason, the \C escape sequence is best
+        avoided.
         PCRE does not allow \C to appear in  lookbehind  assertions  (described
         below),  because  in UTF-8 mode this would make it impossible to calcu-
-Line 3067 
 SQUARE BRACKETS AND CHARACTER CLASSES
+Line 3192 
 SQUARE BRACKETS AND CHARACTER CLASSES
         PCRE  is  compiled  with Unicode property support as well as with UTF-8
         support.
-        Characters that might indicate  line  breaks  (CR  and  LF)  are  never
+        Characters that might indicate line breaks are  never  treated  in  any
-        treated  in  any  special way when matching character classes, whatever
+        special  way  when  matching  character  classes,  whatever line-ending
-        line-ending sequence is in use, and whatever setting of the PCRE_DOTALL
+        sequence is in  use,  and  whatever  setting  of  the  PCRE_DOTALL  and
-        and PCRE_MULTILINE options is used. A class such as [^a] always matches
+        PCRE_MULTILINE options is used. A class such as [^a] always matches one
-        one of these characters.
+        of these characters.
         The minus (hyphen) character can be used to specify a range of  charac-
         ters  in  a  character  class.  For  example,  [d-m] matches any letter
-Line 3203 
 INTERNAL OPTION SETTING
+Line 3328 
 INTERNAL OPTION SETTING
         PCRE extracts it into the global options (and it will therefore show up
         in data extracted by the pcre_fullinfo() function).
-        An option change within a subpattern affects only that part of the cur-
+        An  option  change  within a subpattern (see below for a description of
-        rent pattern that follows it, so
+        subpatterns) affects only that part of the current pattern that follows
+        it, so
           (a(?i)b)c
         matches abc and aBc and no other strings (assuming PCRE_CASELESS is not
-        used).   By  this means, options can be made to have different settings
+        used).  By this means, options can be made to have  different  settings
-        in different parts of the pattern. Any changes made in one  alternative
+        in  different parts of the pattern. Any changes made in one alternative
-        do  carry  on  into subsequent branches within the same subpattern. For
+        do carry on into subsequent branches within the  same  subpattern.  For
         example,
           (a(?i)b|c)
-        matches "ab", "aB", "c", and "C", even though  when  matching  "C"  the
+        matches  "ab",  "aB",  "c",  and "C", even though when matching "C" the
-        first  branch  is  abandoned before the option setting. This is because
+        first branch is abandoned before the option setting.  This  is  because
-        the effects of option settings happen at compile time. There  would  be
+        the  effects  of option settings happen at compile time. There would be
         some very weird behaviour otherwise.
-        The  PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA
+        The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and  PCRE_EXTRA
-        can be changed in the same way as the Perl-compatible options by  using
+        can  be changed in the same way as the Perl-compatible options by using
         the characters J, U and X respectively.
-Line 3235 
 SUBPATTERNS
+Line 3361 
 SUBPATTERNS
           cat(aract|erpillar|)
-        matches one of the words "cat", "cataract", or  "caterpillar".  Without
+        matches  one  of the words "cat", "cataract", or "caterpillar". Without
-        the  parentheses,  it  would  match "cataract", "erpillar" or the empty
+        the parentheses, it would match  "cataract",  "erpillar"  or  an  empty
         string.
-. It sets up the subpattern as  a  capturing  subpattern.  This  means
+.  It  sets  up  the  subpattern as a capturing subpattern. This means
-        that,  when  the  whole  pattern  matches,  that portion of the subject
+        that, when the whole pattern  matches,  that  portion  of  the  subject
         string that matched the subpattern is passed back to the caller via the
-        ovector  argument  of pcre_exec(). Opening parentheses are counted from
+        ovector argument of pcre_exec(). Opening parentheses are  counted  from
-        left to right (starting from 1) to obtain  numbers  for  the  capturing
+        left  to  right  (starting  from 1) to obtain numbers for the capturing
         subpatterns.
-        For  example,  if the string "the red king" is matched against the pat-
+        For example, if the string "the red king" is matched against  the  pat-
         tern
           the ((red|white) (king|queen))
-Line 3254 
 SUBPATTERNS
+Line 3380 
 SUBPATTERNS
         the captured substrings are "red king", "red", and "king", and are num-
         bered 1, 2, and 3, respectively.
-        The  fact  that  plain  parentheses  fulfil two functions is not always
+        The fact that plain parentheses fulfil  two  functions  is  not  always
-        helpful.  There are often times when a grouping subpattern is  required
+        helpful.   There are often times when a grouping subpattern is required
-        without  a capturing requirement. If an opening parenthesis is followed
+        without a capturing requirement. If an opening parenthesis is  followed
-        by a question mark and a colon, the subpattern does not do any  captur-
+        by  a question mark and a colon, the subpattern does not do any captur-
-        ing,  and  is  not  counted when computing the number of any subsequent
+        ing, and is not counted when computing the  number  of  any  subsequent
-        capturing subpatterns. For example, if the string "the white queen"  is
+        capturing  subpatterns. For example, if the string "the white queen" is
         matched against the pattern
           the ((?:red|white) (king|queen))
         the captured substrings are "white queen" and "queen", and are numbered
-and 2. The maximum number of capturing subpatterns is 65535, and  the
+and 2. The maximum number of capturing subpatterns is 65535.
-        maximum  depth  of  nesting of all subpatterns, both capturing and non-
-        capturing, is 200.
-        As a convenient shorthand, if any option settings are required  at  the
+        As  a  convenient shorthand, if any option settings are required at the
-        start  of  a  non-capturing  subpattern,  the option letters may appear
+        start of a non-capturing subpattern,  the  option  letters  may  appear
         between the "?" and the ":". Thus the two patterns
           (?i:saturday|sunday)
           (?:(?i)saturday|sunday)
         match exactly the same set of strings. Because alternative branches are
-        tried  from  left  to right, and options are not reset until the end of
+        tried from left to right, and options are not reset until  the  end  of
-        the subpattern is reached, an option setting in one branch does  affect
+        the  subpattern is reached, an option setting in one branch does affect
-        subsequent  branches,  so  the above patterns match "SUNDAY" as well as
+        subsequent branches, so the above patterns match "SUNDAY"  as  well  as
         "Saturday".
  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, something that Perl  does  not  provide.  The  Python  syntax
+        patterns. This feature was not added to Perl until release 5.10. Python
-        (?P<name>...)  is  used. References to capturing parentheses from other
+        had the feature earlier, and PCRE introduced it at release  4.0,  using
-        parts of the pattern, such as  backreferences,  recursion,  and  condi-
+        the  Python syntax. PCRE now supports both the Perl and the Python syn-
-        tions, can be made by name as well as by number.
+        tax.
-        Names  consist  of  up  to  32 alphanumeric characters and underscores.
+        In PCRE, a subpattern can be named in one of three  ways:  (?<name>...)
-        Named capturing parentheses are still  allocated  numbers  as  well  as
+        or  (?'name'...)  as in Perl, or (?P<name>...) as in Python. References
-        names. The PCRE API provides function calls for extracting the name-to-
+        to capturing parentheses from other parts of the pattern, such as back-
-        number translation table from a compiled pattern. There is also a  con-
+        references,  recursion,  and conditions, can be made by name as well as
-        venience function for extracting a captured substring by name.
+        by number.
+        Names consist of up to  32  alphanumeric  characters  and  underscores.
+        Named  capturing  parentheses  are  still  allocated numbers as well as
+        names, exactly as if the names were not present. The PCRE API  provides
+        function calls for extracting the name-to-number translation table from
+        a compiled pattern. There is also a convenience function for extracting
+        a captured substring by name.
         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
-Line 3308 
 NAMED SUBPATTERNS
+Line 3439 
 NAMED SUBPATTERNS
         both cases you want to extract the abbreviation. This pattern (ignoring
         the line breaks) does the job:
-          (?P<DN>Mon|Fri|Sun)(?:day)?|
+          (?<DN>Mon|Fri|Sun)(?:day)?|
-          (?P<DN>Tue)(?:sday)?|
+          (?<DN>Tue)(?:sday)?|
-          (?P<DN>Wed)(?:nesday)?|
+          (?<DN>Wed)(?:nesday)?|
-          (?P<DN>Thu)(?:rsday)?|
+          (?<DN>Thu)(?:rsday)?|
-          (?P<DN>Sat)(?:urday)?
+          (?<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
-        returns  the  substring  for  the first, and in this example, the only,
+        returns  the  substring  for  the first (and in this example, the only)
         subpattern of that name that matched.  This  saves  searching  to  find
         which  numbered  subpattern  it  was. If you make a reference to a non-
         unique named subpattern from elsewhere in the  pattern,  the  one  that
-Line 3331 
 REPETITION
+Line 3462 
 REPETITION
         following items:
           a literal data character
-          the . metacharacter
+          the dot metacharacter
           the \C escape sequence
           the \X escape sequence (in UTF-8 mode with Unicode properties)
+          the \R escape sequence
           an escape such as \d that matches a single character
           a character class
           a back reference (see next section)
-Line 3373 
 REPETITION
+Line 3505 
 REPETITION
         The quantifier {0} is permitted, causing the expression to behave as if
         the previous item and the quantifier were not present.
-        For  convenience  (and  historical compatibility) the three most common
+        For  convenience, the three most common quantifiers have single-charac-
-        quantifiers have single-character abbreviations:
+        ter abbreviations:
           *    is equivalent to {0,}
           +    is equivalent to {1,}
-Line 3426 
 REPETITION
+Line 3558 
 REPETITION
         which matches one digit by preference, but can match two if that is the
         only way the rest of the pattern matches.
-        If the PCRE_UNGREEDY option is set (an option which is not available in
+        If the PCRE_UNGREEDY option is set (an option that is not available  in
         Perl),  the  quantifiers are not greedy by default, but individual ones
         can be made greedy by following them with a  question  mark.  In  other
         words, it inverts the default behaviour.
-Line 3437 
 REPETITION
+Line 3569 
 REPETITION
         minimum or maximum.
         If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equiv-
-        alent  to Perl's /s) is set, thus allowing the . to match newlines, the
+        alent  to  Perl's  /s) is set, thus allowing the dot to match newlines,
-        pattern is implicitly anchored, because whatever follows will be  tried
+        the pattern is implicitly anchored, because whatever  follows  will  be
-        against  every character position in the subject string, so there is no
+        tried  against every character position in the subject string, so there
-        point in retrying the overall match at any position  after  the  first.
+        is no point in retrying the overall match at  any  position  after  the
-        PCRE normally treats such a pattern as though it were preceded by \A.
+        first.  PCRE  normally treats such a pattern as though it were preceded
+        by \A.
-        In  cases  where  it  is known that the subject string contains no new-
+        In cases where it is known that the subject  string  contains  no  new-
-        lines, it is worth setting PCRE_DOTALL in order to  obtain  this  opti-
+        lines,  it  is  worth setting PCRE_DOTALL in order to obtain this opti-
         mization, or alternatively using ^ to indicate anchoring explicitly.
-        However,  there is one situation where the optimization cannot be used.
+        However, there is one situation where the optimization cannot be  used.
-        When .*  is inside capturing parentheses that  are  the  subject  of  a
+        When  .*   is  inside  capturing  parentheses that are the subject of a
-        backreference  elsewhere in the pattern, a match at the start may fail,
+        backreference elsewhere in the pattern, a match at the start  may  fail
-        and a later one succeed. Consider, for example:
+        where a later one succeeds. Consider, for example:
           (.*)abc\1
-        If the subject is "xyz123abc123" the match point is the fourth  charac-
+        If  the subject is "xyz123abc123" the match point is the fourth charac-
         ter. For this reason, such a pattern is not implicitly anchored.
         When a capturing subpattern is repeated, the value captured is the sub-
-Line 3463 
 REPETITION
+Line 3596 
 REPETITION
           (tweedle[dume]{3}\s*)+
         has matched "tweedledum tweedledee" the value of the captured substring
-        is  "tweedledee".  However,  if there are nested capturing subpatterns,
+        is "tweedledee". However, if there are  nested  capturing  subpatterns,
-        the corresponding captured values may have been set in previous  itera-
+        the  corresponding captured values may have been set in previous itera-
         tions. For example, after
           /(a|(b))+/
-Line 3474 
 REPETITION
+Line 3607 
 REPETITION
  ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS
-        With both maximizing and minimizing repetition, failure of what follows
+        With both maximizing ("greedy") and minimizing ("ungreedy"  or  "lazy")
-        normally causes the repeated item to be re-evaluated to see if  a  dif-
+        repetition,  failure  of what follows normally causes the repeated item
-        ferent number of repeats allows the rest of the pattern to match. Some-
+        to be re-evaluated to see if a different number of repeats  allows  the
-        times it is useful to prevent this, either to change the nature of  the
+        rest  of  the pattern to match. Sometimes it is useful to prevent this,
-        match,  or  to  cause it fail earlier than it otherwise might, when the
+        either to change the nature of the match, or to cause it  fail  earlier
-        author of the pattern knows there is no point in carrying on.
+        than  it otherwise might, when the author of the pattern knows there is
+        no point in carrying on.
         Consider, for example, the pattern \d+foo when applied to  the  subject
         line
-Line 3493 
 ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
+Line 3627 
 ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
         the  means for specifying that once a subpattern has matched, it is not
         to be re-evaluated in this way.
-        If we use atomic grouping for the previous example, the  matcher  would
+        If we use atomic grouping for the previous example, the  matcher  gives
-        give up immediately on failing to match "foo" the first time. The nota-
+        up  immediately  on failing to match "foo" the first time. The notation
-        tion is a kind of special parenthesis, starting with  (?>  as  in  this
+        is a kind of special parenthesis, starting with (?> as in this example:
-        example:
           (?>\d+)foo
-Line 3528 
 ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
+Line 3661 
 ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
         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
-        meaning  or  processing  of  a possessive quantifier and the equivalent
+        meaning  of  a  possessive  quantifier and the equivalent atomic group,
-        atomic group.
+        though there may be a performance  difference;  possessive  quantifiers
+        should be slightly faster.
-        The possessive quantifier syntax is an extension to  the  Perl  syntax.
-        Jeffrey  Friedl originated the idea (and the name) in the first edition
+        The  possessive  quantifier syntax is an extension to the Perl 5.8 syn-
-        of his book.  Mike McCloskey liked it, so implemented it when he  built
+        tax.  Jeffrey Friedl originated the idea (and the name)  in  the  first
-        Sun's Java package, and PCRE copied it from there.
+        edition of his book. Mike McCloskey liked it, so implemented it when he
+        built Sun's Java package, and PCRE copied it from there. It  ultimately
-        When  a  pattern  contains an unlimited repeat inside a subpattern that
+        found its way into Perl at release 5.10.
-        can itself be repeated an unlimited number of  times,  the  use  of  an
-        atomic  group  is  the  only way to avoid some failing matches taking a
+        PCRE has an optimization that automatically "possessifies" certain sim-
+        ple pattern constructs. For example, the sequence  A+B  is  treated  as
+        A++B  because  there is no point in backtracking into a sequence of A's
+        when B must follow.
+        When a pattern contains an unlimited repeat inside  a  subpattern  that
+        can  itself  be  repeated  an  unlimited number of times, the use of an
+        atomic group is the only way to avoid some  failing  matches  taking  a
         very long time indeed. The pattern
           (\D+|<\d+>)*[!?]
-        matches an unlimited number of substrings that either consist  of  non-
+        matches  an  unlimited number of substrings that either consist of non-
-        digits,  or  digits  enclosed in <>, followed by either ! or ?. When it
+        digits, or digits enclosed in <>, followed by either ! or  ?.  When  it
         matches, it runs quickly. However, if it is applied to
           aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
-        it takes a long time before reporting  failure.  This  is  because  the
+        it  takes  a  long  time  before reporting failure. This is because the
-        string  can be divided between the internal \D+ repeat and the external
+        string can be divided between the internal \D+ repeat and the  external
-        * repeat in a large number of ways, and all  have  to  be  tried.  (The
+        *  repeat  in  a  large  number of ways, and all have to be tried. (The
-        example  uses  [!?]  rather than a single character at the end, because
+        example uses [!?] rather than a single character at  the  end,  because
-        both PCRE and Perl have an optimization that allows  for  fast  failure
+        both  PCRE  and  Perl have an optimization that allows for fast failure
-        when  a single character is used. They remember the last single charac-
+        when a single character is used. They remember the last single  charac-
-        ter that is required for a match, and fail early if it is  not  present
+        ter  that  is required for a match, and fail early if it is not present
-        in  the  string.)  If  the pattern is changed so that it uses an atomic
+        in the string.) If the pattern is changed so that  it  uses  an  atomic
         group, like this:
           ((?>\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 sub-
+        It is not possible to have a numerical "forward back  reference"  to  a
-        pattern whose number is 10 or more. However, a back  reference  to  any
+        subpattern  whose  number  is  10  or  more using this syntax because a
-        subpattern  is  possible  using named parentheses (see below). See also
+        sequence such as \50 is interpreted as a character  defined  in  octal.
-        the subsection entitled "Non-printing  characters"  above  for  further
+        See the subsection entitled "Non-printing characters" above for further
-        details of the handling of digits following a backslash.
+        details of the handling of digits following a backslash.  There  is  no
+        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
+        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-
+        tive  or  a negative number, optionally enclosed in braces. These exam-
+        ples are all identical:
+          (ring), \1
+          (ring), \g1
+          (ring), \g{1}
+        A positive number specifies an absolute reference without the ambiguity
+        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,
+        \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
+        joining together fragments that contain references within themselves.
         A  back  reference matches whatever actually matched the capturing sub-
         pattern in the current subject string, rather  than  anything  matching
-Line 3603 
 BACK REFERENCES
+Line 3768 
 BACK REFERENCES
         matches  "rah  rah"  and  "RAH RAH", but not "RAH rah", even though the
         original capturing subpattern is matched caselessly.
-        Back references to named subpatterns use the Python  syntax  (?P=name).
+        Back references to named subpatterns use the Perl  syntax  \k<name>  or
-        We could rewrite the above example as follows:
+        \k'name'  or  the  Python  syntax (?P=name). We could rewrite the above
+        example in either of the following ways:
+          (?<p1>(?i)rah)\s+\k<p1>
           (?P<p1>(?i)rah)\s+(?P=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
           (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". Because there
-        may  be  many  capturing parentheses in a pattern, all digits following
+        may be many capturing parentheses in a pattern,  all  digits  following
-        the backslash are taken as part of a potential back  reference  number.
+        the  backslash  are taken as part of a potential back reference 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
+        used  to  terminate  the back reference. If the PCRE_EXTENDED option is
-        set,  this  can  be  whitespace.  Otherwise an empty comment (see "Com-
+        set, this can be whitespace.  Otherwise an  empty  comment  (see  "Com-
         ments" below) can be used.
-        A back reference that occurs inside the parentheses to which it  refers
+        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
+        fails when the subpattern is first used, so, for example,  (a\1)  never
-        matches.  However, such references can be useful inside  repeated  sub-
+        matches.   However,  such references can be useful inside repeated sub-
         patterns. For example, the pattern
           (a|b\1)+
         matches any number of "a"s and also "aba", "ababbaa" etc. At each iter-
-        ation of the subpattern,  the  back  reference  matches  the  character
+        ation  of  the  subpattern,  the  back  reference matches the character
-        string  corresponding  to  the previous iteration. In order for this to
+        string corresponding to the previous iteration. In order  for  this  to
-        work, the pattern must be such that the first iteration does  not  need
+        work,  the  pattern must be such that the first iteration does not need
-        to  match the back reference. This can be done using alternation, as in
+        to match the back reference. This can be done using alternation, as  in
         the example above, or by a quantifier with a minimum of zero.
  ASSERTIONS
-        An assertion is a test on the characters  following  or  preceding  the
+        An  assertion  is  a  test on the characters following or preceding the
-        current  matching  point that does not actually consume any characters.
+        current matching point that does not actually consume  any  characters.
-        The simple assertions coded as \b, \B, \A, \G, \Z,  \z,  ^  and  $  are
+        The  simple  assertions  coded  as  \b, \B, \A, \G, \Z, \z, ^ and $ are
         described above.
-        More  complicated  assertions  are  coded as subpatterns. There are two
+        More complicated assertions are coded as  subpatterns.  There  are  two
-        kinds: those that look ahead of the current  position  in  the  subject
+        kinds:  those  that  look  ahead of the current position in the subject
-        string,  and  those  that  look  behind  it. An assertion subpattern is
+        string, and those that look  behind  it.  An  assertion  subpattern  is
-        matched in the normal way, except that it does not  cause  the  current
+        matched  in  the  normal way, except that it does not cause the current
         matching position to be changed.
-        Assertion  subpatterns  are  not  capturing subpatterns, and may not be
+        Assertion subpatterns are not capturing subpatterns,  and  may  not  be
-        repeated, because it makes no sense to assert the  same  thing  several
+        repeated,  because  it  makes no sense to assert the same thing several
-        times.  If  any kind of assertion contains capturing subpatterns within
+        times. If any kind of assertion contains capturing  subpatterns  within
-        it, these are counted for the purposes of numbering the capturing  sub-
+        it,  these are counted for the purposes of numbering the capturing sub-
         patterns in the whole pattern.  However, substring capturing is carried
-        out only for positive assertions, because it does not  make  sense  for
+        out  only  for  positive assertions, because it does not make sense for
         negative assertions.
     Lookahead assertions
-Line 3668 
 ASSERTIONS
+Line 3835 
 ASSERTIONS
           \w+(?=;)
-        matches a word followed by a semicolon, but does not include the  semi-
+        matches  a word followed by a semicolon, but does not include the semi-
         colon in the match, and
           foo(?!bar)
-        matches  any  occurrence  of  "foo" that is not followed by "bar". Note
+        matches any occurrence of "foo" that is not  followed  by  "bar".  Note
         that the apparently similar pattern
           (?!foo)bar
-        does not find an occurrence of "bar"  that  is  preceded  by  something
+        does  not  find  an  occurrence  of "bar" that is preceded by something
-        other  than "foo"; it finds any occurrence of "bar" whatsoever, because
+        other than "foo"; it finds any occurrence of "bar" whatsoever,  because
         the assertion (?!foo) is always true when the next three characters are
         "bar". A lookbehind assertion is needed to achieve the other effect.
         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
+        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
+        always matches, so an assertion that requires there not to be an  empty
         string must always fail.
     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 3707 
 ASSERTIONS
+Line 3874 
 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  (at  least  for  5.8),  which
-        requires all branches to match the same length of string. An  assertion
+        requires  all branches to match the same length of string. An assertion
         such as
           (?<=ab(c|de))
-        is  not  permitted,  because  its single top-level branch can match two
+        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 if rewritten to use two top-
         level branches:
           (?<=abc|abde)
-        The  implementation  of lookbehind assertions is, for each alternative,
+        The implementation of lookbehind assertions is, for  each  alternative,
-        to temporarily move the current position back by the  fixed  width  and
+        to  temporarily  move the current position back by the fixed length and
         then try to match. If there are insufficient characters before the cur-
-        rent position, the match is deemed to fail.
+        rent position, the assertion fails.
         PCRE does not allow the \C escape (which matches a single byte in UTF-8
-        mode)  to appear in lookbehind assertions, because it makes it impossi-
+        mode) to appear in lookbehind assertions, because it makes it  impossi-
-        ble to calculate the length of the lookbehind. The \X escape, which can
+        ble  to  calculate the length of the lookbehind. The \X and \R escapes,
-        match different numbers of bytes, is also not permitted.
+        which can match different numbers of bytes, are also not permitted.
-        Atomic  groups can be used in conjunction with lookbehind assertions to
+        Possessive quantifiers can  be  used  in  conjunction  with  lookbehind
-        specify efficient matching at the end of the subject string. Consider a
+        assertions  to  specify  efficient  matching  at the end of the subject
-        simple pattern such as
+        string. Consider a simple pattern such as
           abcd$
-        when  applied  to  a  long string that does not match. Because matching
+        when applied to a long string that does  not  match.  Because  matching
         proceeds from left to right, PCRE will look for each "a" in the subject
-        and  then  see  if what follows matches the rest of the pattern. If the
+        and then see if what follows matches the rest of the  pattern.  If  the
         pattern is specified as
           ^.*abcd$
-        the initial .* matches the entire string at first, but when this  fails
+        the  initial .* matches the entire string at first, but when this fails
         (because there is no following "a"), it backtracks to match all but the
-        last character, then all but the last two characters, and so  on.  Once
+        last  character,  then all but the last two characters, and so on. Once
-        again  the search for "a" covers the entire string, from right to left,
+        again the search for "a" covers the entire string, from right to  left,
         so we are no better off. However, if the pattern is written as
-          ^(?>.*)(?<=abcd)
-        or, equivalently, using the possessive quantifier syntax,
           ^.*+(?<=abcd)
-        there can be no backtracking for the .* item; it  can  match  only  the
+        there  can  be  no backtracking for the .*+ item; it can match only the
-        entire  string.  The subsequent lookbehind assertion does a single test
+        entire string. The subsequent lookbehind assertion does a  single  test
-        on the last four characters. If it fails, the match fails  immediately.
+        on  the last four characters. If it fails, the match fails immediately.
-        For  long  strings, this approach makes a significant difference to the
+        For long strings, this approach makes a significant difference  to  the
         processing time.
     Using multiple assertions
-Line 3768 
 ASSERTIONS
+Line 3931 
 ASSERTIONS
           (?<=\d{3})(?<!999)foo
-        matches "foo" preceded by three digits that are not "999". Notice  that
+        matches  "foo" preceded by three digits that are not "999". Notice that
-        each  of  the  assertions is applied independently at the same point in
+        each of the assertions is applied independently at the  same  point  in
-        the subject string. First there is a  check  that  the  previous  three
+        the  subject  string.  First  there  is a check that the previous three
-        characters  are  all  digits,  and  then there is a check that the same
+        characters are all digits, and then there is  a  check  that  the  same
         three characters are not "999".  This pattern does not match "foo" pre-
-        ceded  by  six  characters,  the first of which are digits and the last
+        ceded by six characters, the first of which are  digits  and  the  last
-        three of which are not "999". For example, it  doesn't  match  "123abc-
+        three  of  which  are not "999". For example, it doesn't match "123abc-
         foo". A pattern to do that is
           (?<=\d{3}...)(?<!999)foo
-        This  time  the  first assertion looks at the preceding six characters,
+        This time the first assertion looks at the  preceding  six  characters,
         checking that the first three are digits, and then the second assertion
         checks that the preceding three characters are not "999".
-Line 3787 
 ASSERTIONS
+Line 3950 
 ASSERTIONS
           (?<=(?<!foo)bar)baz
-        matches  an occurrence of "baz" that is preceded by "bar" which in turn
+        matches an occurrence of "baz" that is preceded by "bar" which in  turn
         is not preceded by "foo", while
           (?<=\d{3}(?!999)...)foo
-        is another pattern that matches "foo" preceded by three digits and  any
+        is  another pattern that matches "foo" preceded by three digits and any
         three characters that are not "999".
  CONDITIONAL SUBPATTERNS
-        It  is possible to cause the matching process to obey a subpattern con-
+        It is possible to cause the matching process to obey a subpattern  con-
-        ditionally or to choose between two alternative subpatterns,  depending
+        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 previous capturing  subpat-
-        tern matched or not. The two possible forms of  conditional  subpattern
+        tern  matched  or not. The two possible forms of conditional subpattern
         are
           (?(condition)yes-pattern)
           (?(condition)yes-pattern|no-pattern)
-        If  the  condition is satisfied, the yes-pattern is used; otherwise the
+        If the condition is satisfied, the yes-pattern is used;  otherwise  the
-        no-pattern (if present) is used. If there are more  than  two  alterna-
+        no-pattern  (if  present)  is used. If there are more than two alterna-
         tives in the subpattern, a compile-time error occurs.
-        There are three kinds of condition. If the text between the parentheses
+        There are four kinds of condition: references  to  subpatterns,  refer-
-        consists of a sequence of digits, or a sequence of alphanumeric charac-
+        ences to recursion, a pseudo-condition called DEFINE, and assertions.
-        ters  and underscores, the condition is satisfied if the capturing sub-
-        pattern of that number or name has previously matched. There is a  pos-
+    Checking for a used subpattern by number
-        sible  ambiguity here, because subpattern names may consist entirely of
-        digits. PCRE looks first for a named subpattern; if it cannot find  one
+        If  the  text between the parentheses consists of a sequence of digits,
-        and  the text consists entirely of digits, it looks for a subpattern of
+        the condition is true if the capturing subpattern of  that  number  has
-        that number, which must be greater than zero.  Using  subpattern  names
+        previously matched.
-        that consist entirely of digits is not recommended.
         Consider  the  following  pattern, which contains non-significant white
         space to make it more readable (assume the PCRE_EXTENDED option) and to
-Line 3836 
 CONDITIONAL SUBPATTERNS
+Line 3998 
 CONDITIONAL SUBPATTERNS
         tern  is  executed  and  a  closing parenthesis is required. Otherwise,
         since no-pattern is not present, the  subpattern  matches  nothing.  In
         other  words,  this  pattern  matches  a  sequence  of non-parentheses,
-        optionally enclosed in parentheses. Rewriting it to use a named subpat-
+        optionally enclosed in parentheses.
-        tern gives this:
+    Checking for a used subpattern by name
+        Perl uses the syntax (?(<name>)...) or (?('name')...)  to  test  for  a
+        used  subpattern  by  name.  For compatibility with earlier versions of
+        PCRE, which had this facility before Perl, the syntax  (?(name)...)  is
+        also  recognized. However, there is a possible ambiguity with this syn-
+        tax, because subpattern names may  consist  entirely  of  digits.  PCRE
+        looks  first for a named subpattern; if it cannot find one and the name
+        consists entirely of digits, PCRE looks for a subpattern of  that  num-
+        ber,  which must be greater than zero. Using subpattern names that con-
+        sist entirely of digits is not recommended.
+        Rewriting the above example to use a named subpattern gives this:
-          (?P<OPEN> \( )?    [^()]+    (?(OPEN) \) )
+          (?<OPEN> \( )?    [^()]+    (?(<OPEN>) \) )
+    Checking for pattern recursion
         If the condition is the string (R), and there is no subpattern with the
-        name R, the condition is satisfied if a recursive call to  the  pattern
+        name  R, the condition is true if a recursive call to the whole pattern
-        or  subpattern  has  been made. At "top level", the condition is false.
+        or any subpattern has been made. If digits or a name preceded by amper-
-        This is a PCRE extension.  Recursive patterns are described in the next
+        sand follow the letter R, for example:
-        section.
+          (?(R3)...) or (?(R&name)...)
+        the  condition is true if the most recent recursion is into the subpat-
+        tern whose number or name is given. This condition does not  check  the
+        entire recursion stack.
+        At  "top  level", all these recursion test conditions are false. Recur-
+        sive patterns are described below.
+    Defining subpatterns for use by reference only
+        If the condition is the string (DEFINE), and  there  is  no  subpattern
+        with  the  name  DEFINE,  the  condition is always false. In this case,
+        there may be only one alternative  in  the  subpattern.  It  is  always
+        skipped  if  control  reaches  this  point  in the pattern; the idea of
+        DEFINE is that it can be used to define "subroutines" that can be  ref-
+        erenced  from elsewhere. (The use of "subroutines" is described below.)
+        For example, a pattern to match an IPv4 address could be  written  like
+        this (ignore whitespace and line breaks):
+          (?(DEFINE) (?<byte> 2[0-4]\d | 25[0-5] | 1\d\d | [1-9]?\d) )
+          \b (?&byte) (\.(?&byte)){3} \b
+        The  first part of the pattern is a DEFINE group inside which a another
+        group named "byte" is defined. This matches an individual component  of
+        an  IPv4  address  (a number less than 256). When matching takes place,
+        this part of the pattern is skipped because DEFINE acts  like  a  false
+        condition.
+        The rest of the pattern uses references to the named group to match the
+        four dot-separated components of an IPv4 address, insisting on  a  word
+        boundary at each end.
+    Assertion conditions
-        If  the  condition  is  not  a sequence of digits or (R), it must be an
+        If  the  condition  is  not  in any of the above formats, it must be an
         assertion.  This may be a positive or negative lookahead or  lookbehind
         assertion.  Consider  this  pattern,  again  containing non-significant
         white space, and with the two alternatives on the second line:
-Line 3882 
 RECURSIVE PATTERNS
+Line 4094 
 RECURSIVE PATTERNS
         unlimited nested parentheses. Without the use of  recursion,  the  best
         that  can  be  done  is  to use a pattern that matches up to some fixed
         depth of nesting. It is not possible to  handle  an  arbitrary  nesting
-        depth.  Perl  provides  a  facility  that allows regular expressions to
+        depth.
-        recurse (amongst other things). It does this by interpolating Perl code
-        in the expression at run time, and the code can refer to the expression
+        For some time, Perl has provided a facility that allows regular expres-
-        itself. A Perl pattern to solve the parentheses problem can be  created
+        sions to recurse (amongst other things). It does this by  interpolating
-        like this:
+        Perl  code in the expression at run time, and the code can refer to the
+        expression itself. A Perl pattern using code interpolation to solve the
+        parentheses problem can be created like this:
           $re = qr{\( (?: (?>[^()]+) | (?p{$re}) )* \)}x;
         The (?p{...}) item interpolates Perl code at run time, and in this case
-        refers recursively to the pattern in which it appears. Obviously,  PCRE
+        refers recursively to the pattern in which it appears.
-        cannot  support  the  interpolation  of Perl code. Instead, it supports
-        some special syntax for recursion of the entire pattern, and  also  for
+        Obviously, PCRE cannot support the interpolation of Perl code. Instead,
-        individual subpattern recursion.
+        it  supports  special  syntax  for recursion of the entire pattern, and
+        also for individual subpattern recursion.  After  its  introduction  in
+        PCRE  and  Python,  this  kind of recursion was introduced into Perl at
+        release 5.10.
-        The  special item that consists of (? followed by a number greater than
+        A special item that consists of (? followed by a  number  greater  than
         zero and a closing parenthesis is a recursive call of the subpattern of
-        the  given  number, provided that it occurs inside that subpattern. (If
+        the given number, provided that it occurs inside that  subpattern.  (If
-        not, it is a "subroutine" call, which is described  in  the  next  sec-
+        not,  it  is  a  "subroutine" call, which is described in the next sec-
-        tion.)  The special item (?R) is a recursive call of the entire regular
+        tion.) The special item (?R) or (?0) is a recursive call of the  entire
-        expression.
+        regular expression.
-        A recursive subpattern call is always treated as an atomic group.  That
+        In  PCRE (like Python, but unlike Perl), a recursive subpattern call is
-        is,  once  it  has  matched some of the subject string, it is never re-
+        always treated as an atomic group. That is, once it has matched some of
-        entered, even if it contains untried alternatives and there is a subse-
+        the subject string, it is never re-entered, even if it contains untried
-        quent matching failure.
+        alternatives and there is a subsequent matching failure.
-        This  PCRE  pattern  solves  the nested parentheses problem (assume the
+        This PCRE pattern solves the nested  parentheses  problem  (assume  the
         PCRE_EXTENDED option is set so that white space is ignored):
           \( ( (?>[^()]+) | (?R) )* \)
-        First it matches an opening parenthesis. Then it matches any number  of
+        First  it matches an opening parenthesis. Then it matches any number of
-        substrings  which  can  either  be  a sequence of non-parentheses, or a
+        substrings which can either be a  sequence  of  non-parentheses,  or  a
-        recursive match of the pattern itself (that is, a  correctly  parenthe-
+        recursive  match  of the pattern itself (that is, a correctly parenthe-
         sized substring).  Finally there is a closing parenthesis.
-        If  this  were  part of a larger pattern, you would not want to recurse
+        If this were part of a larger pattern, you would not  want  to  recurse
         the entire pattern, so instead you could use this:
           ( \( ( (?>[^()]+) | (?1) )* \) )
-        We have put the pattern into parentheses, and caused the  recursion  to
+        We  have  put the pattern into parentheses, and caused the recursion to
-        refer  to them instead of the whole pattern. In a larger pattern, keep-
+        refer to them instead of the whole pattern. In a larger pattern,  keep-
-        ing track of parenthesis numbers can be tricky. It may be  more  conve-
+        ing  track  of parenthesis numbers can be tricky. It may be more conve-
-        nient  to use named parentheses instead. For this, PCRE uses (?P>name),
+        nient to use named parentheses instead. The Perl  syntax  for  this  is
-        which is an extension to the Python syntax that  PCRE  uses  for  named
+        (?&name);  PCRE's  earlier syntax (?P>name) is also supported. We could
-        parentheses (Perl does not provide named parentheses). We could rewrite
+        rewrite the above example as follows:
-        the above example as follows:
+          (?<pn> \( ( (?>[^()]+) | (?&pn) )* \) )
-          (?P<pn> \( ( (?>[^()]+) | (?P>pn) )* \) )
+        If there is more than one subpattern with the same name,  the  earliest
-        This particular example pattern contains nested unlimited repeats,  and
+        one  is used. This particular example pattern contains nested unlimited
-        so  the  use of atomic grouping for matching strings of non-parentheses
+        repeats, and so the use of atomic grouping for matching strings of non-
-        is important when applying the pattern to strings that  do  not  match.
+        parentheses  is  important when applying the pattern to strings that do
-        For example, when this pattern is applied to
+        not match. For example, when this pattern is applied to
           (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa()
-        it  yields "no match" quickly. However, if atomic grouping is not used,
+        it yields "no match" quickly. However, if atomic grouping is not  used,
-        the match runs for a very long time indeed because there  are  so  many
+        the  match  runs  for a very long time indeed because there are so many
-        different  ways  the  + and * repeats can carve up the subject, and all
+        different ways the + and * repeats can carve up the  subject,  and  all
         have to be tested before failure can be reported.
         At the end of a match, the values set for any capturing subpatterns are
         those from the outermost level of the recursion at which the subpattern
-        value is set.  If you want to obtain  intermediate  values,  a  callout
+        value  is  set.   If  you want to obtain intermediate values, a callout
-        function can be used (see the next section and the pcrecallout documen-
+        function can be used (see below and the pcrecallout documentation).  If
-        tation). If the pattern above is matched against
+        the pattern above is matched against
           (ab(cd)ef)
-        the value for the capturing parentheses is  "ef",  which  is  the  last
+        the  value  for  the  capturing  parentheses is "ef", which is the last
-        value  taken  on at the top level. If additional parentheses are added,
+        value taken on at the top level. If additional parentheses  are  added,
         giving
           \( ( ( (?>[^()]+) | (?R) )* ) \)
              ^                        ^
              ^                        ^
-        the string they capture is "ab(cd)ef", the contents of  the  top  level
+        the  string  they  capture is "ab(cd)ef", the contents of the top level
-        parentheses.  If there are more than 15 capturing parentheses in a pat-
+        parentheses. If there are more than 15 capturing parentheses in a  pat-
         tern, PCRE has to obtain extra memory to store data during a recursion,
-        which  it  does  by  using pcre_malloc, freeing it via pcre_free after-
+        which it does by using pcre_malloc, freeing  it  via  pcre_free  after-
-        wards. If  no  memory  can  be  obtained,  the  match  fails  with  the
+        wards.  If  no  memory  can  be  obtained,  the  match  fails  with the
         PCRE_ERROR_NOMEMORY error.
-        Do  not  confuse  the (?R) item with the condition (R), which tests for
+        Do not confuse the (?R) item with the condition (R),  which  tests  for
-        recursion.  Consider this pattern, which matches text in  angle  brack-
+        recursion.   Consider  this pattern, which matches text in angle brack-
-        ets,  allowing for arbitrary nesting. Only digits are allowed in nested
+        ets, allowing for arbitrary nesting. Only digits are allowed in  nested
-        brackets (that is, when recursing), whereas any characters are  permit-
+        brackets  (that is, when recursing), whereas any characters are permit-
         ted at the outer level.
           < (?: (?(R) \d++  | [^<>]*+) | (?R)) * >
-        In  this  pattern, (?(R) is the start of a conditional subpattern, with
+        In this pattern, (?(R) is the start of a conditional  subpattern,  with
-        two different alternatives for the recursive and  non-recursive  cases.
+        two  different  alternatives for the recursive and non-recursive cases.
         The (?R) item is the actual recursive call.
  SUBPATTERNS AS SUBROUTINES
         If the syntax for a recursive subpattern reference (either by number or
-        by name) is used outside the parentheses to which it refers,  it  oper-
+        by  name)  is used outside the parentheses to which it refers, it oper-
-        ates  like  a  subroutine in a programming language. An earlier example
+        ates like a subroutine in a programming language. The "called"  subpat-
+        tern  may  be defined before or after the reference. An earlier example
         pointed out that the pattern
           (sens|respons)e and \1ibility
-Line 3996 
 SUBPATTERNS AS SUBROUTINES
+Line 4214 
 SUBPATTERNS AS SUBROUTINES
           (sens|respons)e and (?1)ibility
         is  used, it does match "sense and responsibility" as well as the other
-        two strings. Such references, if given  numerically,  must  follow  the
+        two strings. Another example is  given  in  the  discussion  of  DEFINE
-        subpattern  to which they refer. However, named references can refer to
+        above.
-        later subpatterns.
         Like recursive subpatterns, a "subroutine" call is always treated as an
-        atomic  group. That is, once it has matched some of the subject string,
+        atomic group. That is, once it has matched some of the subject  string,
-        it is never re-entered, even if it contains  untried  alternatives  and
+        it  is  never  re-entered, even if it contains untried alternatives and
         there is a subsequent matching failure.
+        When a subpattern is used as a subroutine, processing options  such  as
+        case-independence are fixed when the subpattern is defined. They cannot
+        be changed for different calls. For example, consider this pattern:
+          (abc)(?i:(?1))
+        It matches "abcabc". It does not match "abcABC" because the  change  of
+        processing option does not affect the called subpattern.
  CALLOUTS
-Line 4040 
 CALLOUTS
+Line 4266 
 CALLOUTS
         gether. A complete description of the interface to the callout function
         is given in the pcrecallout documentation.
- Last updated: 06 June 2006
+ SEE ALSO
+        pcreapi(3), pcrecallout(3), pcrematching(3), pcre(3).
+ Last updated: 06 December 2006
  Copyright (c) 1997-2006 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 4146 
 EXAMPLE OF PARTIAL MATCHING USING PCRETE
+Line 4377 
 EXAMPLE OF PARTIAL MATCHING USING PCRETE
         The first data string is matched  completely,  so  pcretest  shows  the
         matched  substrings.  The  remaining four strings do not match the com-
         plete pattern, but the first two are partial matches.  The  same  test,
-        using  DFA  matching (by means of the \D escape sequence), produces the
+        using  pcre_dfa_exec()  matching  (by means of the \D escape sequence),
-        following output:
+        produces the following output:
             re> /^?(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)$/
           data> 25jun04\P\D
-Line 4169 
 MULTI-SEGMENT MATCHING WITH pcre_dfa_exe
+Line 4400 
 MULTI-SEGMENT MATCHING WITH pcre_dfa_exe
         When a partial match has been found using pcre_dfa_exec(), it is possi-
         ble to continue the match by  providing  additional  subject  data  and
-        calling  pcre_dfa_exec() again with the PCRE_DFA_RESTART option and the
+        calling  pcre_dfa_exec()  again  with the same compiled regular expres-
-        same working space (where details of the  previous  partial  match  are
+        sion, this time setting the PCRE_DFA_RESTART option. You must also pass
-        stored).  Here  is  an  example  using  pcretest,  where  the \R escape
+        the  same working space as before, because this is where details of the
-        sequence sets the PCRE_DFA_RESTART option and the  \D  escape  sequence
+        previous partial match are stored. Here is an example  using  pcretest,
-        requests the use of pcre_dfa_exec():
+        using the \R escape sequence to set the PCRE_DFA_RESTART option (\P and
+        \D are as above):
             re> /^?(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)$/
           data> 23ja\P\D
-Line 4181 
 MULTI-SEGMENT MATCHING WITH pcre_dfa_exe
+Line 4413 
 MULTI-SEGMENT MATCHING WITH pcre_dfa_exe
           data> n05\R\D
 : n05
-        The  first  call has "23ja" as the subject, and requests partial match-
+        The first call has "23ja" as the subject, and requests  partial  match-
-        ing; the second call  has  "n05"  as  the  subject  for  the  continued
+        ing;  the  second  call  has  "n05"  as  the  subject for the continued
-        (restarted)  match.   Notice  that when the match is complete, only the
+        (restarted) match.  Notice that when the match is  complete,  only  the
-        last part is shown; PCRE does  not  retain  the  previously  partially-
+        last  part  is  shown;  PCRE  does not retain the previously partially-
-        matched  string. It is up to the calling program to do that if it needs
+        matched string. It is up to the calling program to do that if it  needs
         to.
-        This facility can  be  used  to  pass  very  long  subject  strings  to
+        You  can  set  PCRE_PARTIAL  with  PCRE_DFA_RESTART to continue partial
-        pcre_dfa_exec(). However, some care is needed for certain types of pat-
+        matching over multiple segments. This facility can be used to pass very
-        tern.
+        long  subject  strings to pcre_dfa_exec(). However, some care is needed
+        for certain types of pattern.
 . If the pattern contains tests for the beginning or end  of  a  line,
         you  need  to pass the PCRE_NOTBOL or PCRE_NOTEOL options, as appropri-
-Line 4199 
 MULTI-SEGMENT MATCHING WITH pcre_dfa_exe
+Line 4432 
 MULTI-SEGMENT MATCHING WITH pcre_dfa_exe
 .  If  the  pattern contains backward assertions (including \b or \B),
         you need to arrange for some overlap in the subject  strings  to  allow
-        for  this.  For example, you could pass the subject in chunks that were
+        for  this.  For  example, you could pass the subject in chunks that are
 bytes long, but in a buffer of 700 bytes, with the starting  offset
         set to 200 and the previous 200 bytes at the start of the buffer.
-Line 4249 
 MULTI-SEGMENT MATCHING WITH pcre_dfa_exe
+Line 4482 
 MULTI-SEGMENT MATCHING WITH pcre_dfa_exe
         where no string can be a partial match for both alternatives.
- Last updated: 16 January 2006
+ Last updated: 30 November 2006
  Copyright (c) 1997-2006 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 4361 
 COMPATIBILITY WITH DIFFERENT PCRE RELEAS
+Line 4594 
 COMPATIBILITY WITH DIFFERENT PCRE RELEAS
         makes  up  a  compiled pattern was changed for release 5.0. If you have
         any saved patterns that were compiled with  previous  releases  (not  a
         facility  that  was  previously advertised), you will have to recompile
-        them for release 5.0. However, from now on, it should  be  possible  to
+        them for release 5.0 and above.
-        make changes in a compatible manner.
-        Notwithstanding the above, if you have any saved patterns in UTF-8 mode
+        If you have any saved patterns in UTF-8 mode that use  \p  or  \P  that
-        that use \p or \P that were compiled with any release up to and includ-
+        were  compiled  with any release up to and including 6.4, you will have
-        ing 6.4, you will have to recompile them for release 6.5 and above.
+        to recompile them for release 6.5 and above.
- Last updated: 01 February 2006
+        All saved patterns from earlier releases must be recompiled for release
+.0  or  higher,  because  there was an internal reorganization at that
+        release.
+ Last updated: 28 November 2006
  Copyright (c) 1997-2006 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 4382 
 NAME
+Line 4618 
 NAME
  PCRE PERFORMANCE
-        Certain  items  that may appear in regular expression patterns are more
+        Two  aspects  of performance are discussed below: memory usage and pro-
-        efficient than others. It is more efficient to use  a  character  class
+        cessing time. The way you express your pattern as a regular  expression
-        like  [aeiou]  than  a set of alternatives such as (a|e|i|o|u). In gen-
+        can affect both of them.
-        eral, the simplest construction that provides the required behaviour is
-        usually  the  most  efficient.  Jeffrey Friedl's book contains a lot of
-        useful general discussion  about  optimizing  regular  expressions  for
+ MEMORY USAGE
-        efficient  performance. This document contains a few observations about
-        PCRE.
+        Patterns are compiled by PCRE into a reasonably efficient byte code, so
+        that most simple patterns do not use much memory. However, there is one
+        case where memory usage can be unexpectedly large. When a parenthesized
+        subpattern has a quantifier with a minimum greater than 1 and/or a lim-
+        ited  maximum,  the  whole subpattern is repeated in the compiled code.
+        For example, the pattern
+          (abc|def){2,4}
+        is compiled as if it were
+          (abc|def)(abc|def)((abc|def)(abc|def)?)?
+        (Technical aside: It is done this way so that backtrack  points  within
+        each of the repetitions can be independently maintained.)
+        For  regular expressions whose quantifiers use only small numbers, this
+        is not usually a problem. However, if the numbers are large,  and  par-
+        ticularly  if  such repetitions are nested, the memory usage can become
+        an embarrassment. For example, the very simple pattern
+          ((ab){1,1000}c){1,3}
+        uses 51K bytes when compiled. When PCRE is compiled  with  its  default
+        internal  pointer  size of two bytes, the size limit on a compiled pat-
+        tern is 64K, and this is reached with the above pattern  if  the  outer
+        repetition is increased from 3 to 4. PCRE can be compiled to use larger
+        internal pointers and thus handle larger compiled patterns, but  it  is
+        better to try to rewrite your pattern to use less memory if you can.
+        One  way  of reducing the memory usage for such patterns is to make use
+        of PCRE's "subroutine" facility. Re-writing the above pattern as
+          ((ab)(?2){0,999}c)(?1){0,2}
+        reduces the memory requirements to 18K, and indeed it remains under 20K
+        even  with the outer repetition increased to 100. However, this pattern
+        is not exactly equivalent, because the "subroutine" calls  are  treated
+        as  atomic groups into which there can be no backtracking if there is a
+        subsequent matching failure. Therefore, PCRE cannot  do  this  kind  of
+        rewriting  automatically.   Furthermore,  there is a noticeable loss of
+        speed when executing the modified pattern. Nevertheless, if the  atomic
+        grouping  is  not  a  problem and the loss of speed is acceptable, this
+        kind of rewriting will allow you to process patterns that  PCRE  cannot
+        otherwise handle.
+ PROCESSING TIME
+        Certain  items  in regular expression patterns are processed more effi-
+        ciently than others. It is more efficient to use a character class like
+        [aeiou]   than   a   set   of  single-character  alternatives  such  as
+        (a|e|i|o|u). In general, the simplest construction  that  provides  the
+        required behaviour is usually the most efficient. Jeffrey Friedl's book
+        contains a lot of useful general discussion  about  optimizing  regular
+        expressions  for  efficient  performance.  This document contains a few
+        observations about PCRE.
         Using Unicode character properties (the \p,  \P,  and  \X  escapes)  is
         slow,  because PCRE has to scan a structure that contains data for over
-Line 4423 
 PCRE PERFORMANCE
+Line 4715 
 PCRE PERFORMANCE
         take  a  long time to run when applied to a string that does not match.
         Consider the pattern fragment
-          (a+)*
+          ^(a+)*
-        This can match "aaaa" in 33 different ways, and this  number  increases
+        This can match "aaaa" in 16 different ways, and this  number  increases
         very  rapidly  as the string gets longer. (The * repeat can match 0, 1,
-, 3, or 4 times, and for each of those  cases  other  than  0,  the  +
+, 3, or 4 times, and for each of those cases other than 0 or 4, the  +
         repeats  can  match  different numbers of times.) When the remainder of
         the pattern is such that the entire match is going to fail, PCRE has in
         principle  to  try  every  possible  variation,  and  this  can take an
-        extremely long time.
+        extremely long time, even for relatively short strings.
         An optimization catches some of the more simple cases such as
-Line 4452 
 PCRE PERFORMANCE
+Line 4744 
 PCRE PERFORMANCE
         In many cases, the solution to this kind of performance issue is to use
         an atomic group or a possessive quantifier.
- Last updated: 28 February 2005
+ Last updated: 20 September 2006
- Copyright (c) 1997-2005 University of Cambridge.
+ Copyright (c) 1997-2006 University of Cambridge.
  ------------------------------------------------------------------------------
-Line 4667 
 AUTHOR
+Line 4959 
 AUTHOR
         Philip Hazel
         University Computing Service,
-        Cambridge CB2 3QG, England.
+        Cambridge CB2 3QH, England.
  Last updated: 16 January 2006
  Copyright (c) 1997-2006 University of Cambridge.
-Line 4762 
 MATCHING INTERFACE
+Line 5054 
 MATCHING INTERFACE
              number of sub-patterns, "i"th captured sub-pattern is
              ignored.
+        CAVEAT: An optional sub-pattern that does  not  exist  in  the  matched
+        string  is  assigned  the  empty  string. Therefore, the following will
+        return false (because the empty string is not a valid number):
+           int number;
+           pcrecpp::RE::FullMatch("abc", "[a-z]+(\d+)?", &number);
         The matching interface supports at most 16 arguments per call.  If  you
         need    more,    consider    using    the    more   general   interface
         pcrecpp::RE::DoMatch. See pcrecpp.h for the signature for DoMatch.
+ QUOTING METACHARACTERS
+        You can use the "QuoteMeta" operation to insert backslashes before  all
+        potentially  meaningful  characters  in  a string. The returned string,
+        used as a regular expression, will exactly match the original string.
+          Example:
+             string quoted = RE::QuoteMeta(unquoted);
+        Note that it's legal to escape a character even if it  has  no  special
+        meaning  in  a  regular expression -- so this function does that. (This
+        also makes it identical to the perl function  of  the  same  name;  see
+        "perldoc    -f    quotemeta".)    For   example,   "1.5-2.0?"   becomes
+        "1\.5\-2\.0\?".
  PARTIAL MATCHES
         You can use the "PartialMatch" operation when you want the  pattern  to
-Line 4978 
 REPLACING PARTS OF STRINGS
+Line 5293 
 REPLACING PARTS OF STRINGS
  AUTHOR
         The C++ wrapper was contributed by Google Inc.
-        Copyright (c) 2005 Google Inc.
+        Copyright (c) 2006 Google Inc.
  ------------------------------------------------------------------------------
-Line 5108 
 PCRE DISCUSSION OF STACK USAGE
+Line 5423 
 PCRE DISCUSSION OF STACK USAGE
         quantifier  is  used  to stop any backtracking into the runs of non-"<"
         characters, but that is not related to stack usage.
+        This example shows that one way of avoiding stack problems when  match-
+        ing long subject strings is to write repeated parenthesized subpatterns
+        to match more than one character whenever possible.
         In environments where stack memory is constrained, you  might  want  to
         compile  PCRE to use heap memory instead of stack for remembering back-
         up points. This makes it run a lot more slowly, however. Details of how
         to do this are given in the pcrebuild documentation.
-        In Unix-like environments, there is not often a problem with the stack,
+        In  Unix-like environments, there is not often a problem with the stack
-        though the default limit on stack size varies from  system  to  system.
+        unless very long strings are involved,  though  the  default  limit  on
-        Values  from 8Mb to 64Mb are common. You can find your default limit by
+        stack  size  varies  from system to system. Values from 8Mb to 64Mb are
-        running the command:
+        common. You can find your default limit by running the command:
           ulimit -s
-        The effect of running out of stack is often SIGSEGV,  though  sometimes
+        Unfortunately, the effect of running out of  stack  is  often  SIGSEGV,
-        an error message is given. You can normally increase the limit on stack
+        though  sometimes  a more explicit error message is given. You can nor-
-        size by code such as this:
+        mally increase the limit on stack size by code such as this:
           struct rlimit rlim;
           getrlimit(RLIMIT_STACK, &rlim);
-Line 5144 
 PCRE DISCUSSION OF STACK USAGE
+Line 5463 
 PCRE DISCUSSION OF STACK USAGE
         recursion. Thus, if you want to limit your  stack  usage  to  8Mb,  you
         should  set  the  limit at 16000 recursions. A 64Mb stack, on the other
         hand, can support around 128000 recursions. The pcretest  test  program
-        has  a command line option (-S) that can be used to increase its stack.
+        has a command line option (-S) that can be used to increase the size of
+        its stack.
- Last updated: 29 June 2006
+ Last updated: 14 September 2006
  Copyright (c) 1997-2006 University of Cambridge.
  ------------------------------------------------------------------------------

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