Merging simple map-based environment configuration

gistfile1.clj

(def base-config
  {
  :value "some value"
  })

(defn- merge-cfg-item
  [base-item override-item]
  (cond 
    (and (every? map? [base-item override-item]) (not (contains? override-item :replace-all!)))
       (merge-with merge-cfg-item base-item override-item) 
    (and (every? map? [base-item override-item]) (contains? override-item :replace-all!))
       (dissoc override-item :replace-all!)
     :else override-item))

(defn merge-cfg 
  [base-cfg override-cfg]
  (merge-with merge-cfg-item base-cfg override-cfg))

(def ^{:private true} region-config
  (if-let [region (System/getProperty "region")]
    (merge-cfg base-config 
              (read-string (slurp (io/input-stream (io/resource (apply str "conf/" region))))))
    base-config))

(defn get-cfg 
  [& kws]
  (get-in region-config ks))