Assuming that these are true sets, i.e., no element is repeated within the same set, Set::Scalar has what you need (from the synopsis):

use Set::Scalar;
$s = Set::Scalar->new;
$s->insert('a', 'b');
$s->delete('b');
$t = Set::Scalar->new('x', 'y', $z);
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Given the set objects, you can perfom various operation on the sets to derive relations:

    $u = $s->union($t);
    $i = $s->intersection($t);
    $d = $s->difference($t);
    $e = $s->symmetric_difference($t);
    $v = $s->unique($t);
    $c = $s->complement;
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difference can be used to test for subsets and symmetric difference can be used as a kind of distance metric.

Update: fixed a typo.