No sooner are sitcoms pronounced dead, again, than they begin popping up all over, like Whac-a-Moles. This year we have been and will be getting a passel of relationship comedies built around interrelated contrasting sets of couples (and sometimes singles), usually packaged in groups of three, a la “Modern Family,” whose success surely helped turn these lights green. There are perhaps more of them than the market can bear, but if any have to go, I would rather it not be “Perfect Couples.”