preFIX. Not quite sure if "l AND r" but "l OR r". So I am not sure if you can process them simultaniously (if that was your intention).
Edit: much simpler and pretty straight forward if you just need an invert option on both Terry West`s Out! (somewhere in the middle of the page). Actually a lot of his plug ins have this option but this one looks like the "most functional" for this task.