Perl: How to get the 'use VERSION' number

Question

Is there a special variable or a function which gives me the number of use VERSION (in this case 5.12.0) when running the script?

#!/usr/bin/env perl 
use warnings;
use 5.12.0;

Answer 1

I just quickly checked feature.pm code - the version itself is not stored anywhere. Alex's answer already showed how to test particular features that results from the call.

Also note that use VERSION can be called on several places (in modules for instance).

One hypothetical option would be to override use and record the version number somewhere for inspection.

Edit: Some poking in the hook direction:

use version; # for version parsing
use subs 'require';
BEGIN {
    sub require {
        warn "use ",version->parse($_[0]);
        # ... emulate original require
    };
}

use 5.12.0;

This limited example reports the version specified, but for real use it would have to be much more robust.

Answer 2

You can, during compile time, poke about in the hints variable (${^H}) (where dragons lurk) and look into the hints hash (%{^H}) (where dragons lurk, but in a public documented sort of way), this will let you know which specific features are enabled. I don't know how to work out if specifically a feature bundle, or all given features, were requested:

perl -le "use feature qw(:5.12); BEGIN{print $^H;print foreach keys %^H}"
133376
feature_unicode
feature_say
feature_state
feature_switch

perl -le "use 5.12.0; BEGIN{print $^H;print foreach keys %^H}"
134914
feature_unicode
feature_say
feature_state
feature_switch