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Full Discussion: q with Perl Regex
Top Forums Shell Programming and Scripting q with Perl Regex Post 302217934 by KevinADC on Thursday 24th of July 2008 12:49:18 AM
Old 07-24-2008
Quote:
Originally Posted by cbkihong
Actually, not even /(.)\1/ is correct. In Perl, you should use /(.)$1/. The former syntax is there for compatibility with I think awk or sed but that should in general not be used in Perl, because Perl has more uses of backslash that may interfere with backtracking.
That is not correct. Using \1 is perfectly good perl code. \1 and $1 really have two seperate uses. See the link I posted in my previous post. A short test shows they do not do the same thing:

Code:
$_ = 'foobar';
if (/(.)$1/) {
   print "\$1 = $1","\n";
}	
if (/(.)\1/) {
   print "\\1 = $1";
}

output:

Code:
$1 = f
\1 = o

 

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Text::Glob(3)						User Contributed Perl Documentation					     Text::Glob(3)

NAME
Text::Glob - match globbing patterns against text SYNOPSIS
use Text::Glob qw( match_glob glob_to_regex ); print "matched " if match_glob( "foo.*", "foo.bar" ); # prints foo.bar and foo.baz my $regex = glob_to_regex( "foo.*" ); for ( qw( foo.bar foo.baz foo bar ) ) { print "matched: $_ " if /$regex/; } DESCRIPTION
Text::Glob implements glob(3) style matching that can be used to match against text, rather than fetching names from a filesystem. If you want to do full file globbing use the File::Glob module instead. Routines match_glob( $glob, @things_to_test ) Returns the list of things which match the glob from the source list. glob_to_regex( $glob ) Returns a compiled regex which is the equivalent of the globbing pattern. glob_to_regex_string( $glob ) Returns a regex string which is the equivalent of the globbing pattern. SYNTAX
The following metacharacters and rules are respected. "*" - match zero or more characters "a*" matches "a", "aa", "aaaa" and many many more. "?" - match exactly one character "a?" matches "aa", but not "a", or "aaa" Character sets/ranges "example.[ch]" matches "example.c" and "example.h" "demo.[a-c]" matches "demo.a", "demo.b", and "demo.c" alternation "example.{foo,bar,baz}" matches "example.foo", "example.bar", and "example.baz" leading . must be explictly matched "*.foo" does not match ".bar.foo". For this you must either specify the leading . in the glob pattern (".*.foo"), or set $Text::Glob::strict_leading_dot to a false value while compiling the regex. "*" and "?" do not match / "*.foo" does not match "bar/baz.foo". For this you must either explicitly match the / in the glob ("*/*.foo"), or set $Text::Glob::strict_wildcard_slash to a false value with compiling the regex. BUGS
The code uses qr// to produce compiled regexes, therefore this module requires perl version 5.005_03 or newer. AUTHOR
Richard Clamp <richardc@unixbeard.net> COPYRIGHT
Copyright (C) 2002, 2003, 2006, 2007 Richard Clamp. All Rights Reserved. This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. SEE ALSO
File::Glob, glob(3) perl v5.18.2 2017-10-06 Text::Glob(3)
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