...
	my @union = my @isect = my @diff = ();
	my %union = my %isect = ();
	my %count = ();
	my $e;
	
	foreach $e (@array1, @array2)
	{
		$count{$e}++
	}
	
	foreach $e (keys %count)
	{
		push(@union, $e);
		
		if ($count{$e} == 2)
		{
			push @isect, $e;
		}
		else
		{
			push @diff, $e;
		}
	}
	
	$listbox->insert('end', @diff); # Ausgabe in Listbox (Perl/TK)
...