use Set::Scalar;
    $s = Set::Scalar->new;
    $s->insert('a', 'b');
    $s->delete('b');
    $t = Set::Scalar->new('x', 'y', $z);

    $u = $s->union($t);
    $i = $s->intersection($t);
    $d = $s->difference($t);
    $e = $s->symmetric_difference($t);
    $v = $s->unique($t);
    $c = $s->complement;