I've used MLDBM with Storable over DB_File a few times. It is perfectly fine as long as you don't need to do searches through the value part of the data--for that you really want a relational solution. But as long as you're just doing key lookups, it's wonderful.

MLDBM is not necessarily a drop-in replacement, however. The biggest "gotcha" is that you cannot assign a value directly to a non-top-level element. That is, you can't do this to a MLDBM tied hash: $hash{foo}{bar}{baz} = 'stuff';

You must instead do this:

$tmp = $hash{foo};
$tmp->{bar}{baz} = 'stuff';
$hash{foo} = $tmp;
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