fn.clj

;; Declare a function
(defn fun1 [] (println 1))

;; And a hash that would capture that function
(def h {:key fun1})
;; => {:key #<user$fun1 user$fun1@5e540696>}
 
;; Now, check out the value of the key
(:key h)
;; => #<user$fun1 user$fun1@5e540696>

;; Run the reference of function
((:key h))
;; That's println:
;; => 1
;; nil

;; Redefine the function:
(defn fun1 [] (println 2))
;; => #'user/fun1
 
;; Run it!
((:key h))
;; That's println:
;; => 1
;; nil
 
;; Compare references:
fun1
;; => #<user$fun1 user$fun1@3494e2d2>
 
(:key h)
;; => #<user$fun1 user$fun1@5e540696>


;; In order to avoid it, use #'
(def h {:key #'fun1})
;; That fixes everything. If you don't want to keep writing #' everywhere,
;; and you can afford abstracting things away, use macro:
 
(defmacro by-reference [a]
  `(#'~a))
 
;; Of course I mean use #' within your own macro, no sense replacing pretty #' with `by-reference`.