trim-0

(defn trim-0
  "Trim away all extra 0 in front of a number represented as a string.
   00123 -> 123, 00000 -> 0"
  [text]
  (loop [l text]
    (let [x  (first l)
          xs (rest l)]
      (cond
        (= x \0)  (recur xs)
        (= x nil) "0"
        :else (clojure.string/join l)))))