Simple stack implementation in Clojure

core.clj

(defn new-stack
  []
  (atom []))

(defn pushv [*stack value]
  (when (nil? value)
    (throw (ex-info "nil is not allowed" {:value value})))
  (swap! *stack conj value)
  @*stack)

(defn popv [*stack]
  (let [v (peek @*stack)]
    (when-not (nil? v) 
      (swap! *stack pop))
    v))

(def s (new-stack))

(pushv s 1)
(pushv s 2)
(pushv s 3)

(popv s)