NAME
Perl::Critic::Policy::Subroutines::ProhibitUnderscorePrivateSubs - Make a private sub lexical, rather than private by a leading underscore.
VERSION
version 0.001
Perl::Critic::Policy::Subroutines::ProhibitUnderscorePrivateSubs
It's a common convention in perl to have a leading underscore mean that a sub is private, but nothing enforces it. Any code can call Some::Module::_helper, a subclass can override it without knowing, and a test that calls it tests the implementation instead of the documented interface. A lexical sub is private in fact: nothing outside its scope can use it.
sub _helper { ... } # reported
_helper(@args);
my sub helper { ... } # perl 5.26 and later
helper(@args);
my $helper = sub { ... }; # any perl
$helper->(@args);
$self->$helper(@args); # called as a methodPROHIBITED
sub _helper { ... }
sub _helper; # a forward declaration
sub Some::Module::_helper { ... } # the last part of the name counts
our sub _helper { ... } # our is a package subALLOWED
my sub helper { ... }
state sub helper { ... }
my $helper = sub { ... };
sub helper { ... } # public, and named so
sub _build_thing { ... } # when allow names it, see PARAMETERSPARAMETERS
allow is a list of names, separated by whitespace, that the policy leaves alone. Use it for a name that another module requires to be a package sub, such as a builder that an object system looks up by name:
[Subroutines::ProhibitUnderscorePrivateSubs]
allow = _build_thing _trigger_thingCAVEATS
A method that a subclass overrides is not private, whatever its name says. Give it a name without the underscore, and document it as the interface between the class and its subclasses.
A lexical sub cannot be tested from outside its scope. That is the point: test the public sub that calls it.
A sub installed through a glob, such as *_helper = sub { ... }, is not seen.
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-prohibitunderscoreprivatesubs/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>
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.