originally refheap.com/97879

essentially.clj

(defmacro essentially
  "Like letfn, but with the bindings at the end. Connotes that the
bindings are not important for the core logic, just for logging,
metrics, debugging etc. Recommend using footnote-looking bindings such
as *0, *1, *2 or even Unicode daggers if you are super-brave.
This is like Haskell's `where`. Thanks to amalloy for the pointer; no
blame attaches to him, though."
  [& args]
  `(letfn ~(last args)
     ~@(butlast args)))

(defn do-a-thing
  [foo bar baz]
  (essentially
    (let [grovel (+ foo (‡ (bar)))]
      (baz grovel))
    [(‡ [v] (println "Bar was:" v) v)]))

;; => (do-a-thing 1 (constantly 2) -)
;; Bar was: 2
;; -3