gistfile1.txt

(progn
  (defsubst spooky-action-at-a-distance ()
    (let ((a (concat "a" "bc")))
      (store-substring a 0 "123")))

  (defun foo ()
    (spooky-action-at-a-distance)
    (concat "ab" "c"))

  (byte-compile 'foo)
  (foo))