Hash to disc: what's good and fast these days?

[Roger Burton West]

There are lots of modules that let me tie a hash to some sort of
database: BerkeleyDB, TokyoCabinet, CDB, and so on. Is there anything
that's aware of Perl data structures and will let me tie a _multi-level_
hash to a disc file? If so, what's the best option? (I was thinking of
YAML, but it's too slow for big data sets...)