sub fredekin {
        my ($a,$b,$c) = @_;
        return (($a) ? ($a,$c,$b) : ($a,$b,$c));
    }

    sub toffoli {
        my @list = @_;
        
        my $tail = pop @list;
        my $state = 0;
        
        for my $i (@list) {
            $state++ if ($i);
        }
        if ($state == @list) {
            $tail = ($tail) ? 0 : 1;
        }
        return ((@list, $tail));
    }