Thank you very much for posting these, I have a nagging feeling I'll need to refer to this post at some point in the extremely near future. (:
Perhaps someone could figure out how to extend the DBI into a sub-module that abstracted the database issue? It could check for environmentals and depending on what it found, execute the database-specific code from there... it would be only sort of non-portable then, kind of like DBD::xxx ... hmmm... too early, should probably drink some coffee before I go spouting off like this. =P
