Perl::Critic::Policy::RegularExpressions::ProhibitFixedStringMatches(3)

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

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) 2007-2023 Chris Dolan

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