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;
[download]

From your other post, however, it seems like you are interested in a more specialized form of set, that is integer ranges or spans. In this case, check out the module Set::IntSpan:

  use Set::IntSpan qw(grep_set map_set);

  $set_spec = "1-20000";
  $set    = new   Set::IntSpan $set_spec;

  $set_spec = "1-14192,14194,14196-14221";
  $u_set = union      $set $set_spec;
  $i_set = intersect  $set $set_spec;
  $x_set = xor        $set $set_spec;
  $d_set = diff       $set $set_spec;
  $c_set = complement $set;
[download]