Let me first say that I've never had to do this, but here are several suggestions:

Would suggest that you try renaming one DBD module. Since you're working with multiple boxen, port collision wouldn't be a problem. ENV variables might.

Or, try writing two scripts, one with the path to O7's DBD and the other with O9's, and call them as transfer scripts from your main program.

Take STDIN as SQL and pass it to DBI/DBD, and respond to STDOUT. You'd have to pass the data arrays by SHM, filesystem, or something like that.

Alternately, you could run them as daemons on the individual boxen, and just pass SQL and the stringified response back.