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Perinci::Sub::DepChecker - Check dependencies from 'deps' property


This document describes version 0.128 of Perinci::Sub::DepChecker (from Perl distribution Perinci-Sub-DepChecker), released on 2023-11-16.


 use Perinci::Spec::DepChecker qw(check_deps dep_satisfy_rel list_mentioned_dep_clauses);

 my $err = check_deps($meta->{deps});
 print "Dependencies not met: $err" if $err;

 print "We need to prepare foo"
     if dep_satisfy_rel('foo', $meta->{deps}) =~ /^(?:must|might)$/;


The 'deps' spec clause adds information about subroutine dependencies. This module performs check on it.

This module is currently mainly used by Perinci::Sub::Wrapper.


None is exported by default, but every function is exportable.

check_deps($deps) => ERRSTR

Check dependencies. Will in turn call various checkdep_NAME() subroutines. Return empty string if all dependencies are met, or a string containing an error message stating a dependency error.


 my $err = check_deps({env=>'DEBUG'});

Will check environment variable DEBUG. If true, will return an empty string. Otherwise will set $err with something like Environment variable DEBUG not set/true.

Another example:

 my $err = check_deps({ all=>[{env=>"A"}, {env=>"B", prog=>"bc"}] });

The above will check environment variables A, B, as well as program bc. All dependencies must be met (because we use the and metaclause).

To support a custom dependency named NAME, just define checkdep_NAME subroutine in Perinci::Sub::DepChecker package which accepts a value and should return an empty string on success or an error message string.

dep_satisfy_rel($name, $deps) => STR

Check dep satisfication relationship, i.e. whether dependency named $name must be satisfied in $deps. Due to all, any, and none clauses, this needs to be checked recursively and might yield an inconclusive answer ("maybe").

Return "must" if $name definitely must be satisfied in $deps, "must not" if definitely not, "" if need not be satisfied (dep clause does not exist in deps), "impossible" if condition is impossible to be satisfied (due to conflicts), "might" if dep might need to be satisfied (but might also not).


 dep_satisfy_rel('env', {env=>"A"})              # => "must"
 dep_satisfy_rel('a', {all=>[{a=>1}, {b=>1}]})   # => "must"
 dep_satisfy_rel('a', {b=>2})                    # => ""
 dep_satisfy_rel('a', {none=>[{a=>1}, {b=>1}]})  # => "must not"
 dep_satisfy_rel('c', {none=>[{a=>1}, {b=>1}]})  # => ""
 dep_satisfy_rel('a', {any=>[{a=>1}, {b=>1}]})   # => "might"
 dep_satisfy_rel('a', {all=>[{a=>1},
                             {none=>[{a=>1}]}]}) # => "impossible"

This function is useful if we want to prepare something that "must" or "might" be needed, or want to avoid preparing something that "must not" be present.

list_mentioned_dep_clauses($deps) => ARRAYREF

List all dep clauses mentioned in $deps. The returned array is not sorted alphabetically, so you will have to do it yourself if you need it sorted.


 list_mentioned_dep_clauses({any=>[{a=>1}, {b=>1}]}) # => [qw/any a b/]


Please visit the project's homepage at


Source repository is at



'deps' section in Rinci::function


perlancar <>


Steven Haryanto <>


To contribute, you can send patches by email/via RT, or send pull requests on GitHub.

Most of the time, you don't need to build the distribution yourself. You can simply modify the code, then test via:

 % prove -l

If you want to build the distribution (e.g. to try to install it locally on your system), you can install Dist::Zilla, Dist::Zilla::PluginBundle::Author::PERLANCAR, Pod::Weaver::PluginBundle::Author::PERLANCAR, and sometimes one or two other Dist::Zilla- and/or Pod::Weaver plugins. Any additional steps required beyond that are considered a bug and can be reported to me.


This software is copyright (c) 2023, 2022, 2015, 2014, 2013, 2012, 2011 by perlancar <>.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.


Please report any bugs or feature requests on the bugtracker website

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.