;; https://stackoverflow.com/questions/36039840/elisp-bind-a-lambda-in-a-let-and-execute-it

(let ((f (lambda (s) (message s))))
  ;; f is a variable so should be treated as such.
  (funcall f "This works.")

  ;; f is not a function so cannot be found if called like this.
  (f "This does not work."))