my $primaryFeatures = {
    'foo', ['fool', 'food', 'foot'],
    'bar', ['barricade'],
};

##</code><code>##

for my $element (@$value) {
    print "($key, $element)\n";
}

##</code><code>##

use strict;
use warnings;

my %primaryFeatures = (
    foo => [qw{fool food foot}],
    bar => [qw{barricade}],
);

for my $key (keys %primaryFeatures) {
    for my $element (@{$primaryFeatures{$key}}) {
        print "($key, $element)\n";
    }
}

##</code><code>##

(bar, barricade)
(foo, fool)
(foo, food)
(foo, foot)