in reply to using keys on hash of hash

Although it has been corrected, I think nobody so far told you that you made two syntax errors. The first is to use parenthesis instead of curly brackets. This constructs a list, not a hash reference. In scalar context that yields the last item of the list, which is the second half of your hash.

Note that the "fat arrows" => do not influence the type of the thing you are constructing, it's merely a weird looking comma that automagically quotes the thing on its LHS. So you could even write things like this:

my @list = foo => bar => 'baz';

The second error (this time a real syntax error that perl chokes on) is that you are missing a comma before h2.