Slight augment to Clojure's update-in function

gistfile1.clj

;; the following function works much like clojure.core/update-in, but
;; also works in the case that the nested data structure being traversed
;; includes a list from which you want to get the first element. 
;; it's woefully incapable of handling anything more complex, as the 
;; aforementioned use case was the only one I had when I wrote it.
(defn update-in+
  "Similar to clojure.core/update-in, except coll may include lists and                                                                                                           
  key* may include references to clojure.core/first so that lists in coll                                                                                                         
  can be traversed."
  [coll key* f & arg*]
  (letfn [($update-in+ [coll key*]
            (if-let [key (first key*)]
              (let [key* (next key*)]
                (if (identical? key clojure.core/first)
                    (conj (next coll) ($update-in+ (first coll) key*))
                    (assoc coll key ($update-in+ (get coll key) key*))))
              (apply f coll arg*)))]
    ($update-in+ coll key*)))

;; used for early testing in clojure.tools.cps to only apply the CPS 
;; transform to the first overload of a fn expression. 
;; since the CPS transformer can support multi-overload fn expressions, 
;; this is no longer used for clojure.tools.cps, but it seemed like it 
;; should be saved for posterity.