Well-Grounded Java Developer: Account example revised

account.clj

(defn make-account [name balance]
  {:name name :balance balance})

(defn withdraw [account n]
     (update-in  account  [:balance] - n))

; Single-Treaded withdraw/loop
(loop [a (make-account "Ben" 5000)]
  (Thread/sleep 1)
  (if (pos? (:balance a))
    (recur (withdraw a 1))
    a))

(defn account-depositor [account-ref]
  (Thread/sleep 1)
  (if (dosync
       (if (pos? (:balance @account-ref))
         (pos? (:balance (alter account-ref withdraw 1)))))
    (recur account-ref)))

(def my-acc (ref (make-account "Ben" 5000)))

(apply pcalls (repeat 5 (partial account-depositor my-acc)))