core.clj

(use 'clojure.walk)

(def my-vec [[1 2] [3 4]])
(def simple-vec [1 2])

; mapv approach
(defn rand-walk [x a] (+ x (* a (- (rand) (rand)))))
(defn rwalk->vec [v a] (mapv #(rand-walk % a) v))

; working
(mapv #(rand-walk % 3) simple-vec)
(rwalk->vec [1 2] 3)
(mapv #(rwalk->vec % 3) my-vec)

; postwalk approach
(defn rand-walk 
  ([x] (+ x (* 2 (- (rand) (rand)))))
  ([& more] (println more)))

; not working :(
(postwalk #(rwalk->vec % 3) my-vec)