perl::critic::policy::regularexpressions::prohibitescapedmetacha(3) [centos man page]

Perl::Critic::Policy::RegularExpressions::ProhibitEscapeUseraContributedPerl::Critic::Policy::RegularExpressions::ProhibitEscapedMetacharacters(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

perl v5.16.3							    2014Perl::Critic::Policy::RegularExpressions::ProhibitEscapedMetacharacters(3)

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Perl::Critic::Policy::RegularExpressions::ProhibitUnusedUseruContributed Perl Perl::Critic::Policy::RegularExpressions::ProhibitUnusedCapture(3pm)

NAME

       Perl::Critic::Policy::RegularExpressions::ProhibitUnusedCapture - Only use a capturing group if you plan to use the captured value.

AFFILIATION

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

DESCRIPTION

       Perl regular expressions have multiple types of grouping syntax.  The basic parentheses (e.g. "m/(foo)/") captures into the magic variable
       $1.  Non-capturing groups (e.g. "m/(?:foo)/" are useful because they have better runtime performance and do not copy strings to the magic
       global capture variables.

       It's also easier on the maintenance programmer if you consistently use capturing vs. non-capturing groups, because that programmer can tell
       more easily which regexps can be refactored without breaking surrounding code which may use the captured values.

CONFIGURATION

       This Policy is not configurable except for the standard options.

CAVEATS

   "qr//" interpolation
       This policy can be confused by interpolation of "qr//" elements, but those are always false negatives.  For example:

	   my $foo_re = qr/(foo)/;
	   my ($foo) = m/$foo_re (bar)/x;

       A human can tell that this should be a violation because there are two captures but only the first capture is used, not the second.  The
       policy only notices that there is one capture in the regexp and remains happy.

   "@-", "@+", $LAST_MATCH_START and $LAST_MATCH_END
       This policy will only recognize capture groups referred to by these variables if the use is subscripted by a literal integer.

   $^N and $LAST_SUBMATCH_RESULT
       This policy will not recognize capture groups referred to only by these variables, because there is in general no way by static analysis to
       determine which capture group is referred to.  For example,

	   m/ (?: (A[[:alpha:]]+) | (Nd+) ) (?{$foo=$^N}) /smx

       makes use of the first capture group if it matches, or the second capture group if the first does not match but the second does.

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

perl v5.14.2							    2012-06-07Perl::Critic::Policy::RegularExpressions::ProhibitUnusedCapture(3pm)

Linux and UNIX Man Pages

perl::critic::policy::regularexpressions::prohibitescapedmetacha(3) [centos man page]

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