Persistance is relativly easy to do, and it sounds as if you're most of the way there.

In a non-persistant world I manage my database connections via a database handler. Basically I can call and "cache" any amount of statements and handles I wish.

In a persistant world, as you rightly mention the database handles are kept open by mod_perl. From memory mod_perl will go and check the connection is still up, and if not it will bring it back up. So in effect mod_perl manages your connections for you. (I've read the theory, but not used it IRL yet, so I'll stand corrected here).