Tim Bunce sent me an e-mail earlier this week where he pointed out that it's very rare that you need to call finish() explicitly. If you're querying a large result set and only fetch a couple of rows, you could call it to free up memory.

I don't have the DBI book with me, or I'd quote chapter and verse, but I know there's something about it in the DBI manpage. You can probably get by without it here, unless you're doing something exotic. (You might also like prepare_cached()).