Turn a StringBuilder into a Clojure Function Take 2

builder.clj

(defn builder
  ([^StringBuilder sb]
     (fn
       ([] (.toString sb))
       ([& args]
          (doseq [arg args]
            (.append sb arg)))))
  ([] (builder (StringBuilder.))))

(comment
This version allows you to invoke the returned function with no args to call 
toString on the StringBuilder. It also provides a no args call to builder that
creates a new StringBuilder for you.

Example...

user=> (def foo (builder))
#'user/foo
user=> (apply foo (interpose " " '(hello world)))
nil
user=> (foo)
"hello world"

)