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revision 461 by ph10, Mon Oct 5 10:59:35 2009 UTC revision 518 by ph10, Tue May 18 15:47:01 2010 UTC
# Line 6  PCRE - Perl-compatible regular expressio Line 6  PCRE - Perl-compatible regular expressio
6  .sp  .sp
7  This document describes the differences in the ways that PCRE and Perl handle  This document describes the differences in the ways that PCRE and Perl handle
8  regular expressions. The differences described here are with respect to Perl  regular expressions. The differences described here are with respect to Perl
9  5.10.  5.10/5.11.
10  .P  .P
11  1. PCRE has only a subset of Perl's UTF-8 and Unicode support. Details of what  1. PCRE has only a subset of Perl's UTF-8 and Unicode support. Details of what
12  it does have are given in the  it does have are given in the
# Line 93  page. Line 93  page.
93  strings when part of a pattern is repeated. For example, matching "aba" against  strings when part of a pattern is repeated. For example, matching "aba" against
94  the pattern /^(a(b)?)+$/ in Perl leaves $2 unset, but in PCRE it is set to "b".  the pattern /^(a(b)?)+$/ in Perl leaves $2 unset, but in PCRE it is set to "b".
95  .P  .P
96  11. PCRE does support Perl 5.10's backtracking verbs (*ACCEPT), (*FAIL), (*F),  11. PCRE's handling of duplicate subpattern numbers and duplicate subpattern
 (*COMMIT), (*PRUNE), (*SKIP), and (*THEN), but only in the forms without an  
 argument. PCRE does not support (*MARK).  
 .P  
 12. PCRE's handling of duplicate subpattern numbers and duplicate subpattern  
97  names is not as general as Perl's. This is a consequence of the fact the PCRE  names is not as general as Perl's. This is a consequence of the fact the PCRE
98  works internally just with numbers, using an external table to translate  works internally just with numbers, using an external table to translate
99  between numbers and names. In particular, a pattern such as (?|(?<a>A)|(?<b)B),  between numbers and names. In particular, a pattern such as (?|(?<a>A)|(?<b)B),
# Line 107  would not be possible to distinguish whi Line 103  would not be possible to distinguish whi
103  names map to capturing subpattern number 1. To avoid this confusing situation,  names map to capturing subpattern number 1. To avoid this confusing situation,
104  an error is given at compile time.  an error is given at compile time.
105  .P  .P
106  13. PCRE provides some extensions to the Perl regular expression facilities.  12. PCRE provides some extensions to the Perl regular expression facilities.
107  Perl 5.10 includes new features that are not in earlier versions of Perl, some  Perl 5.10 includes new features that are not in earlier versions of Perl, some
108  of which (such as named parentheses) have been in PCRE for some time. This list  of which (such as named parentheses) have been in PCRE for some time. This list
109  is with respect to Perl 5.10:  is with respect to Perl 5.10:
# Line 164  Cambridge CB2 3QH, England. Line 160  Cambridge CB2 3QH, England.
160  .rs  .rs
161  .sp  .sp
162  .nf  .nf
163  Last updated: 04 October 2009  Last updated: 12 May 2010
164  Copyright (c) 1997-2009 University of Cambridge.  Copyright (c) 1997-2010 University of Cambridge.
165  .fi  .fi
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