pure perl multi-level hash/array DBM that supports transactions

 DBM::Deep is an unique flat-file database module, written in pure perl. True
 multi-level hash/array support (unlike MLDBM, which is faked), hybrid OO /
 tie() interface, cross-platform FTPable files, ACID transactions, and is quite
 fast. Can handle millions of keys and unlimited levels without significant
 slow-down. Written from the ground-up in pure perl -- this is NOT a wrapper
 around a C-based DBM.