Add flashy flashing to Emacs eval calls.

.emacs snippet

  (require 'nrepl-eval-sexp-fu)
  (setq nrepl-eval-sexp-fu-flash-duration 0.25)
  
  (defadvice lisp-eval-region (around lisp-eval-region-flash activate)
    "Flash any calls to lisp-eval-region (and the functions that depend on it, like lisp-eval-defun)."
    (let* ((start (ad-get-arg 0))
           (end (ad-get-arg 1))
           (flasher (nrepl-eval-sexp-fu-flash (cons start end)))
           (hi (cadr flasher))
           (unhi (caddr flasher)))
      (nrepl-eval-sexp-fu-flash-doit-simple '(lambda () ad-do-it) hi unhi)))

Prerequisite

M-x package-install RET nrepl-eval-sexp-fu

Some might call this mere eye candy, but I actually find the visual feedback very useful.