Nested from flat

gistfile1.clj

(def data {:b--name "B", :a--id 1, :b--id 2, :a--name "A"})

(defn transform [data delimiter]
  (reduce (fn [acc [k v]]
    (let [[f-k s-k] (-> k (name) (str/split delimiter))]
      (assoc-in acc [(keyword f-k) (keyword s-k)] v))) {} data))

(transform data #"--") ;; {:a {:name "A", :id 1}, :b {:id 2, :name "B"}}

(defn transform [data delimiter]
  (reduce (fn [acc [k v]]
    (let [key-strs (-> k (name) (str/split delimiter))]
      (assoc-in acc (mapv keyword key-strs) v))) {} data))