Repeatedly execute a function with side effects with certain period while a reference evaluates to true

tick-while.clj

;; Based on
;; http://bjeanes.com/2012/09/call-clojure-function-on-a-timer
;; Example:
;; (def flag (atom true))
;; (tick-while flag 1000 (fn [s] (println (str s ":" (System/currentTimeMillis)))) "Time")
;; wait for some time and 
;; (swap! flag (fn [_] false))

(defn tick-while
  "Executes the function f (side-effects) with args every t ms until p-ref de-references to false."
  [p-ref t f  & args]
  (letfn [(the-f [] #(apply f args))
          (call-seq [] (lazy-seq (when @p-ref (cons (the-f) (call-seq) ))))]
    (doseq [ff (call-seq)]
      (ff)
      (Thread/sleep t))))