Macro mimicking imperative assignment in Clojure

;; Source:
(defmacro binder [& body]
   (let [[tobind lexpr] (split-at (dec (count body)) body)
         binded (vec (mapcat (fn [e]
                  (if (and (list? e) (= 'bind (first e)))
                     [(second e) (last e)]
                     ['_ e]
                     ))
                  tobind ))]
     `(let ~binded
         ~(first lexpr)
      )))


;; Example:
(binder
  (println 1)
  (bind a 2)
  (println a)
  (bind a 3)
  (println a)
  (bind b 1)
  (println (+ a b)))
=>
1
2
3
4