Hammana, hammana, hammana (who knows how it's supposed to spelled) is an expression which was current in the 1960s (FM's tipping his hand), and was popular among adolescents and among college students. It has a variety of meanings, and the meaning is usually understood in context. In writing, without being able to see FM's mug (thank Dog for some favors), body language, gestures, etc., it's difficult to know what he meant. But i'm assuming he meant, "Oh yeah? big deal (eyes rolling)."