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Manual Reference Pages  -  PERL::CRITIC::POLICY::REGULAREXPRESSIONS::PROHIBITFIXEDSTRINGMATCHES (3)

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NAME

Perl::Critic::Policy::RegularExpressions::ProhibitFixedStringMatches - Use "eq" or hash instead of fixed-pattern regexps.

CONTENTS

AFFILIATION

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

DESCRIPTION

A regular expression that matches just a fixed set of constant strings is wasteful of performance and is hard on maintainers. It is much more readable and often faster to use eq or a hash to match such strings.



    # Bad
    my $is_file_function = $token =~ m/\A (?: open | close | read ) \z/xms;

    # Faster and more readable
    my $is_file_function = $token eq open ||
                           $token eq close ||
                           $token eq read;



For larger numbers of strings, a hash is superior:



    # Bad
    my $is_perl_keyword =
        $token =~ m/\A (?: chomp | chop | chr | crypt | hex | index
                           lc | lcfirst | length | oct | ord | ... ) \z/xms;

    # Better
    Readonly::Hash my %PERL_KEYWORDS => map {$_ => 1} qw(
        chomp chop chr crypt hex index lc lcfirst length oct ord ...
    );
    my $is_perl_keyword = $PERL_KEYWORD{$token};



Conway also suggests using lc() instead of a case-insensitive match.

    VARIANTS

This policy detects both grouped and non-grouped strings. The grouping may or may not be capturing. The grouped body may or may not be alternating. \A and \z are always considered anchoring which ^ and $ are considered anchoring is the m regexp option is not in use. Thus, all of these are violations:



    m/^foo$/;
    m/\A foo \z/x;
    m/\A foo \z/xm;
    m/\A(foo)\z/;
    m/\A(?:foo)\z/;
    m/\A(foo|bar)\z/;
    m/\A(?:foo|bar)\z/;



Furthermore, this policy detects violations in m//, s/// and qr// constructs, as you would expect.

CONFIGURATION

This Policy is not configurable except for the standard options.

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

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perl v5.20.3 PERL::CRITIC::POLICY::REGULAREXPRESSIONS::PROHIBITFIXEDSTRINGMATCHES (3) 2016-04-03

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