(def ^:dynamic *some-var* 0) ; The ** aren't needed to make this dynamic, but ^:dynamic is.

(defn use-var []
  (println *some-var*)) ; Refers to the value of #'*some-var*
  
(binding [*some-var* 1] ; Sets #'*some-var* to be 1 within the binding form
  (println *some-var*) ; Refers to value of #'*some-var*
  (use-var))