Perl::Critic::Policy::Subroutines::ProhibitUnusedPrivateSubroutines - Prevent unused private subroutines.


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


By convention Perl authors (like authors in many other languages) indicate private methods and variables by inserting a leading underscore before the identifier. This policy catches such subroutines which are not used in the file which declares them.

This module defines a 'use' of a subroutine as a subroutine or method call to it (other than from inside the subroutine itself), a reference to it (i.e. my $foo = \&_foo), a goto to it outside the subroutine itself (i.e. goto &_foo), or the use of the subroutine's name as an even-numbered argument to use overload.


You can define what a private subroutine name looks like by specifying a regular expression for the private_name_regex option in your .perlcriticrc:

    private_name_regex = _(?!_)\w+

The above example is a way of saying that subroutines that start with a double underscore are not considered to be private. (Perl::Critic, in its implementation, uses leading double underscores to indicate a distribution-private subroutine -- one that is allowed to be invoked by other Perl::Critic modules, but not by anything outside of Perl::Critic.)

You can configure additional subroutines to accept by specifying them in a space-delimited list to the allow option:

    allow = _bar _baz

These are added to the default list of exemptions from this policy. So the above allows sub _bar {} and sub _baz {}, even if they are not referred to in the module that defines them.

You can allow a whole class or subroutine names by defining a regular expression that matches allowed names.

    allow_name_regex = _build_\w+

You can configure this policy not to check private subroutines declared in a file that uses one or more particular named modules. This allows you to, for example, exclude unused private subroutine checking in classes that are roles.

    skip_when_using = Moose::Role Moo::Role Role::Tiny


This policy is derived from Perl::Critic::Policy::Subroutines::ProtectPrivateSubs, which looks at the other side of the problem.


Does not forbid sub Foo::_foo{} because it does not know (and can not assume) what is in the Foo package.

Does not respect the scope caused by multiple packages in the same file. For example a file:

    package Foo;
    sub _is_private { print "A private sub!"; }

    package Bar;

Will not trigger a violation even though Foo::_is_private is not called. Similarly, skip_when_using currently works on a file level, not on a package scope level.




Chris Dolan <>


Copyright (c) 2009-2021 Thomas R. Wyant, III.

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.