(defn greeting
    ([]     (greeting "World"))
    ([msg]  (str "Hello, " msg exclamation ))
    ([msg1, msg2](str msg1 ", " msg2 exclamation ))
 )

(greeting "Good morning" "Clojure")

;; For testing
(assert (= "Hello, World!" (greeting)))
(assert (= "Hello, Clojure!" (greeting "Clojure")))
(assert (= "Good morning, Clojure!" (greeting "Good morning" "Clojure")))