Welcome to the CHICKEN Scheme pasting service

(use matchable)

(define as-l '(((1 2) . (3 4))))

(define want '(1 2))
(define this '(1 2))

(match (assoc this as-l)
  (#f 'is-false)
  (`(want . ,tail) tail)
  ((head . tail) 'recurse))