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PerlPerl::Critic::PoliUserRContributedsPerlsDocumentationapedMetacharacters(3)

NAME
       Perl::Critic::Policy::RegularExpressions::ProhibitEscapedMetacharacters
       - Use character classes for literal meta-characters instead of escapes.

AFFILIATION
       This Policy is part of the core Perl::Critic distribution.

DESCRIPTION
       Ever heard of leaning toothpick syndrome?  That comes from writing
       regular expressions that	match on characters that are significant in
       regular expressions.  For example, the expression to match four forward
       slashes looks like:

	   m/\/\/\/\//;

       Well, this policy doesn't solve that problem (write it as "m{////}"
       instead!) but solves a related one.  As seen above, the escapes make
       the expression hard to parse visually.  One solution is to use
       character classes.  You see, inside of character	classes, the only
       characters that are special are "\", "]", "^" and "-", so you don't
       need to escape the others.  So instead of the following loose IPv4
       address matcher:

	   m/ \d+ \. \d+ \. \d+	\. \d+ /x;

       You could write:

	   m/ \d+ [.] \d+ [.] \d+ [.] \d+ /x;

       which is	certainly more readable, if less recognizable prior the
       publication of Perl Best	Practices.  (Of	course,	you should really use
       Regexp::Common::net to match IPv4 addresses!)

       Specifically, this policy forbids backslashes immediately prior to the
       following characters:

	   { } ( ) . * + ? | #

       We make special exception for "$" because "/[$]/" turns into
       "/[5.008006/" for Perl 5.8.6.  We also make an exception	for "^"
       because it has special meaning (negation) in a character	class.
       Finally,	"[" and	"]" are	exempt,	of course, because they	are awkward to
       represent in character classes.

       Note that this policy does not forbid unnecessary escaping.  So go
       ahead and (pointlessly) escape "!" characters.

CONFIGURATION
       This Policy is not configurable except for the standard options.

BUGS
       Perl treats "m/[#]/x" in	unexpected ways.  I think it's a bug in	Perl
       itself, but am not 100% sure that I have	not simply misunderstood...

       This part makes sense:

	   "#f"	=~ m/[#]f/x;	 # match
	   "#f"	=~ m/[#]a/x;	 # no match

       This doesn't:

	   $qr	= qr/f/;
	   "#f"	=~ m/[#]$qr/x; # no match

       Neither does this:

	   print qr/[#]$qr/x;  # yields	'(?x-ism:[#]$qr
				       )'

CREDITS
       Initial development of this policy was supported	by a grant from	the
       Perl Foundation.

AUTHOR
       Chris Dolan <cdolan@cpan.org>

COPYRIGHT
       Copyright (c) 2007-2011 Chris Dolan.  Many rights reserved.

       This program is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself.  The full text of this license can
       be found	in the LICENSE file included with this module

perlPerl::Critic::Policy::RegularExpressions::ProhibitEscapedMetacharacters(3)

NAME | AFFILIATION | DESCRIPTION | CONFIGURATION | BUGS | CREDITS | AUTHOR | COPYRIGHT

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