recursive power set

my $n = 5;
print "P({1..$n)={",join(",",map { "{".join(",",@$_)."}" } P(1..$n)),"}\n";

sub P(@) {
    return [] unless (@_);
    my $x = shift @_;
    return (P(@_), map { [ $x, @$_] } P(@_));
}