An oldie: https://ashwinram.org/1986/01/28/a-short-ballad-dedicated-to-the-growt...

waterhouse 88 days ago | parent | context | favorite | on: Hofstadter on Lisp (1983)

Describes the evolution from:

  (cdr (assq key a-list))

to:

  (let ((val (assq key a-list)))
     (cond ((not (null? val)) (cdr val))
           (else nil)))