Your $x is still just a hash reference, and you can treat it like one, although doing so breaks encapsulation and is therefore not recommended. What this means is that you can just say keys %{$x} and get the keys. You can also say $x->{test} and access the "test" key.

By the way, "my $self = ()" is equivalent to "my $self = undef". I think you mean "my $self = {}".