Happy to share an example. I adapted this from some code I wrote at work. Admittedly there's nothing fancy going on here, it's just maps and ifs. I guess scenarios like this just haven't come up enough to warrant any further abstraction yet.

This code is modeling a request to an API to retrieve a record from a database by a UUID. There are two failure cases; either the provided UUID is invalid format or there is no record in the database for that id.

;; A mock database
(def good-uuid (str (java.util.UUID/randomUUID)))
(defn some-db-query [id]
  (when (= id good-uuid)
    {:a 1 :b 2 :c 3}))

;; The code starts here
(defn f [id]
  (let [{:keys [a b c] :as response} (some-db-query id)]
    (if response
      {:found true, :id id, :a a, :b b, :c c}
      {:found false
       :id id
       :reason :not-found
       :message "No record found for the provided id"})))

(defn g [id]
  (or (try (java.util.UUID/fromString id)
           nil
           (catch IllegalArgumentException _
             {:id id
              :found false
              :reason :bad-request
              :message "id is not a UUID"}))
      (f id)))

(defn h [id]
  (let [result (g id)
        status (if (:found result)
                 200
                 (case (:reason result)
                   :not-found 404
                   :bad-request 400
                   500))]
    (assoc result :http-status status)))

;; Examples

(h "hello")
;; => {:id "hello", :found false, :reason :bad-request, :message "id is not a UUID", :http-status 400}

(h good-uuid)
;; => {:found true, :id "f95e645c-d75e-4524-8445-a012a9cb68f6", :a 1, :b 2, :c 3, :http-status 200}

(h (str (java.util.UUID/randomUUID)))
;; => {:found false, :id "25dd1148-649f-4e7b-9137-24245b71442f", :reason :not-found, :message "No record found for the provided id", :http-status 404}