in reply to compound structure? 4way-hash

You can use a subroutine:

get_info(mac=>'0494944545', want=>'file');

If you really need a hash, transform the subroutine into a hash using "tie".

$hash{mac_04994994_file};

(hint) Use split("_") to separate the words. It is much easier than simulating a hash-of-hashes.