The module has a simple interface and is easy to use. It seems to work quite well.
Alas, the documentation is sloppily formatted with an uncommented minimal example (that's missing an important use statement).
It also has no tied interface (which would make it really easy to plug into some existing applications that I have), and for that matter has a poor OO interface: store, fetch and exists with no delete, clear, first_key or next_key methods. (There is a method to return all the keys, but it's not documented.)
It also prototypes the subroutines, which means that you have to use parenthesis in method calls. Yuck.
If it weren't for the interface, I'd give it 4 stars.