The emacs lisp code
(defun my-pretty-lambda ()
  "make some word or string show as pretty Unicode symbols"
  (setq prettify-symbols-alist
        '(("lambda" . 955))))

(add-hook 'paredit-mode-hook 'my-pretty-lambda)
(global-prettify-symbols-mode 1)The emacs lisp code:
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switch to the *scratch* buffer
start slime and evaluate the following form:
(let ((xs '((a . '(λ (s) s))))) xs)