NAME
Perl::Critic::Policy::RegularExpressions::ProhibitIneffectiveModifiers - Write a regex modifier only where it changes what the regex does.
VERSION
version 0.001
Perl::Critic::Policy::RegularExpressions::ProhibitIneffectiveModifiers
A reader takes each modifier on a regex as a statement about what it does. /g says it can match more than once, /i that case matters to it, /m that it anchors lines, and /o that it interpolates something that is compiled once. Where the pattern cannot do that, the modifier is a statement that is not true, and the reader has to work out that it is not:
$name =~ s/^\s+//g; # reported: ^ matches once
$name =~ s/^\s+//;
next unless $line =~ m/\A\d+\z/i; # reported: digits have no case
next unless $line =~ m/\A\d+\z/;PROHIBITED
s/^\s+//g # /g, anchored at the start: it matches once
s/\A\s+//g # \A as well as ^
m/\A(\w+)/g # in a match as well
s/\s+\z//g # anchored at the end, and it cannot match empty
s/x$//g # $ without /m, and it cannot match a newline alone
s/,\Z//g # \Z is the same as $ without /m
s/\A\s+//gm # /m does not change \A, and has no ^ or $ to change
m/\d+/i # /i, and nothing has a case
m/[!-@]/i # nor does a range without a letter in it
qr/\d/i # a compiled regex keeps its own modifiers
m/foo/m # /m, and no ^ or $
m/\Afoo\z/m # \A, \z and \Z are not line anchors
m/foo/o # /o, and nothing to interpolate
s/foo/$bar/o # /o compiles the pattern, not the replacementALLOWED
s/^\s+//gm # ^ under /m is the start of every line
m/^key: .*$/mg # several lines of one form
s/\s+$//g # \s can match the final newline alone, see CAVEATS
s/b*\z//g # can match empty, so twice at the end
s/$/!/g # "a\n" has two places for $ without /m
s/.$//sg # . under /s can match the final newline alone
m/\A\s*/gc # /c keeps pos() for the next match
m/\Ga/g # \G is where the last match stopped
s/\Aa|b//g # alternation: b is not anchored
s/\A$prefix//g # interpolation may bring an alternation
m/[!-~]/i # a range with letters in it
m/\x{df}/i # sharp s matches SS under /i
m/\p{Lu}/i # a property matches the other case under /i
m/(\d)\1/i # a backreference compares without case
m/$word/i # interpolation may bring letters
m/a(?=$)/m # a line anchor anywhere counts
m/$record/m # interpolation may bring ^ and $
m/$r/g # where $r = qr/^key: .*$/m keeps its own /m
m/$x/o # /o with something to compile once
m/a/s # /s, /x and /a are never reported, see CAVEATSCAVEATS
/s, /x, /xx, /a and /aa are never reported. The policies RegularExpressions::RequireDotMatchAnything, RegularExpressions::RequireExtendedFormatting and RegularExpressions::RequireDefault ask for them on every regex, so they are written where they change nothing. RegularExpressions::RequireLineBoundaryMatching asks for /m in the same way; with that policy on, turn this one off, or the two disagree about every regex without ^ or $.
Only a modifier written on the regex is reported. A modifier from use re in scope is a default for the file, not a choice made for this regex, so it is not reported. It still counts toward what the pattern means, so under use re '/m', s/^\s+//g is not reported.
/g at the end of the string is reported only where the policy can tell that the pattern cannot match twice. Before \z that means it cannot match the empty string, so something in it has to match at least one character. Before $, or \Z, without /m, there are two places to end, at the final newline and after it, so something in it has to match a character that is not a newline. The policy does not reason about greediness, so s/\s+$//g, which matches once, is not reported.
m//g in scalar context sets pos() where it stops, and the next \G starts there. When a match anchored at the start is there for that, write /gc, which says so, or say ## no critic (ProhibitIneffectiveModifiers).
A regex that interpolates a variable is not checked for /g, /i or /m. The variable can bring an alternation, a letter or a line anchor, and the policy cannot see what it holds.
METHODS
supported_parameters
default_severity
default_themes
applies_to
violates
BUGS
Please report any bugs or feature requests on the bugtracker website https://github.com/teodesian/perl-critic-policy-prohibitineffectivemodifiers/issues
When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.
AUTHORS
Current Maintainers:
George S. Baugh <george@troglodyne.net>
CONTRIBUTOR
troglodyne-bot <morpheus@troglodyne.net>
COPYRIGHT AND LICENSE
Copyright (c) 2026 Troglodyne LLC
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.