(if (= (* 2 2) 4) (print "if-then-else: equal") (print "if-then-else: non equal"))
(if (= (* 2 2) 6) (print "if-then-else: non equal") (print "if-then-else: i don't know"))
; ==> if-then-else: equal
; ==> if-then-else: i don't know