Clojure cond语句

// 
(ns clojure.examples.hello
   (:gen-class))

;; This program displays Hello World
(defn Example []
   (def x 5)
   (cond
      (= x 5) (println "x is 5")
      (= x 10)(println "x is 10")
      :else (println "x is not defined")))
(Example)