sub permutations 
{
	my $bag = $_[0];
	
	if (is_empty_list($bag))
	{
		return [[]];
	}
	
	my $perms = [];

	foreach my $elem (@$bag)
	{
		foreach my $perm (@{permutations(remove($elem, $bag, 1))})
		{
			unshift(@{$perm}, $elem);
			push(@{$perms}, $perm);
		}
	}
	
	return $perms;
}