... if you're willing to use MLDBM with care.

Too many times, I've seen beginners tie %a, then wonder why setting $a{$b} works but why setting $a{$b}{$c} doesn't actually change anything on disk. Yes, it's mysterious. Too much of the underlying mechanism pokes through. For all the hassles it is, I recommend instead that you simply do your own load/save on an entire hash kept in memory.

-- Randal L. Schwartz, Perl hacker