Whatever you're doing, STOP IT NOW . . . . And watch this movie. If you've already seen it, you won't object to my saying "watch it again!" We've all been indignant with Agatha Christie and others for presenting a mystery but withholding vital clues to drag out the suspense. Neil Simon takes all the famous writers to task in this hilarious, uproariously funny farce. For many years after watching this movie, my wife and I would exchange the "Benson Mum" "Bensonmum, Sir." If you don't recognize that, it has been too long since you've watched "Murder By Death."