Advanced Syntax

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<PROGRAM> uses Perl-compatible regular expressions.(PCRE) library. The library is a set of functions that implement regular expression pattern matching using the same syntax and semantics as Perl 5, with just a few differences. The current implementation corresponds to Perl 5.005. The syntax and semantics of the regular expressions supported by the PCRE are described in this chapter. For Perl 5 regular expression syntax, read the Perl regular expressions man page at



†        Meta-Characters

†        Backslash

†        Circumflex and Dollar

†        Full Stop (Period, Dot)

†        Square Brackets

†        Vertical Bar

†        Internal Option Setting

†        Subpatterns

†        Repetition

†        Back References

†        Assertions

†        Once-Only Subpatterns

†        Conditional Subpatterns

†        Comments

†        Performance

†        Limitiations

†        Differences From Perl


The PCRE Library, which is open source software, and these chapters (Regular Expressions Syntax (Advanced)) are written by Philip Hazel <>, University of Cambridge Computing Service, Cambridge, England. Phone: +44 1223 334714. Copyright © 1997-1999 University of Cambridge


Regular expressions are also described in the Perl documentation and in a number of other books, some of which have copious examples. Jeffrey Friedl's "Mastering Regular Expressions", published by O'Reilly (ISBN 1-56592-257-3), covers them in great detail. The description here is intended as reference documentation.