Is there a way to find out how much memory a hash is consuming? Preferably a fast way?

I don't want to know how many elements the hash has ( scalar(keys(%hash))), I want to know how much memory it consumes. If there is a way to find this without iterating through the entire hash that would be best.

I tried to RTFM, but I didn't find this info. If this is somewhere obvious and I missed it, please tell me where I should have looked.

Thanks!
-Pileofrogs