Selective backup script

I've seen a couple backup scripts that query the metadata to determine the list of databases to back up.  I like this approach, but have a few databases which don't get backed up for various reasons, e.g. testing databases which we'd prefer to recreate on the off chance we loose them, rather than have using up time/disk for backup.  Might there be a way to tag those databases somehow so the backup script knows to skip them?  I'd rather not hard code the list in the script.