maybe you're right.

It is hard to believe that you beat Berkeley DB by 300%.
but - assume that you have good and honest numbers, and indeed you've outbeat the BerkeleyDB.
It could be that you implemented a subset of DB that suits you and therefore you could win by not implementing some "difficult" places that Berkeley DB must have implemented. I do not know.

But generally - you do not gain speed by re-implementing robust C library into pure-perl.

Another point - external C library is safer to use with respect to fact that it is better tested - by larger user base etc.

Ok, your mileage varies in a sence that you win in your way,
but generally - this way just does not win.

Regards,
Vadim.