What exactly is going on here?

gistfile1.clj

(defn mk-executor-transfer-fn [batch-transfer->worker]
  (fn this
    ([task tuple block? ^List overflow-buffer]
      (if (and overflow-buffer (not (.isEmpty overflow-buffer)))
        (.add overflow-buffer [task tuple])
        (try-cause
          (disruptor/publish batch-transfer->worker [task tuple] block?)
        (catch InsufficientCapacityException e
          (if overflow-buffer
            (.add overflow-buffer [task tuple])
            (throw e))
          ))))
    ([task tuple overflow-buffer]
      (this task tuple (nil? overflow-buffer) overflow-buffer))
    ([task tuple]
      (this task tuple nil)
      )))