my @a = qw(a b c d e f);
my @b = qw(c d e f g h);
my ($only_a, $only_b, $both, $either) = listy(\@a, \@b);
print "only in a: @$only_a\n";
print "only in b: @$only_b\n";
print "both: @$both\n";
print "either: @$either\n";

sub listy {
  my %tmp1;
  for (0..1) {
    for my $k (@{$_[$_]}) {
      $tmp1{$k} .= $_;
    }
  }
  my %tmp2;
  while (my($k, $v) = each %tmp1) {
    push @{$tmp2{$v}}, $k;
  }
  return @tmp2{"0", "1", "01"}, [keys %tmp1]; 
}