http://www.perlmonks.org?node_id=3891

Q&A > Data Structures > How do I make a hash of hashes? - Answer contributed by da w00t

If it was declared as a named hash of multiple dimensions, you may access it like $hash{foo}->{bar}->{beer}="free";, or like this: $hash{foo}{bar}{beer}="free"; if you prefer to drop the arrows.

If it's an anonymous hash held in a hash reference, you access it like this:

$r_hash->{foo}{bar}{beer}= "free";