loop.clj

(defn get-route [route-map req]
  (loop [routes (keys route-map)]
    (let [route (first routes)]
      (if (route-matches route req)
        (get route-map route)
        (recur (rest routes))))))

; This is one way
(defn get-route [route-map req]
  (when-let [[route fun] (first (filter #(route-matches (first %) req) route-map))]
     fun))

; With a default:

; This is one way to provide defaults
(defn get-route 
  ([route-map req default] 
    (let [[route fun] (first (filter #(route-matches (first %) req) route-map))]
      (or fun default)))
  ([route-map req] (get-route route-map reg nil)))