LOGIC says anything outside of coitus is perversion. The anatomical function is axiomatic.
That assumes that the sole purpose of sex is reproduction. In Judaism, one of the purposes of sex is to bring the husband and wife closer together -- thus sex is encouraged, even in couples where it cannot lead to reproduction.
As such, if a married couple is into some non-reproductive sexual act that brings them closer together... well, maybe it's perverision, but then, God Bless Perversion!
It is amazing that Man is the only creature that hides his genitalia, but is also the only creature that has the most trouble with it...
Genesis (1:27, 2:18).