(define (foo1 x1 #!optional x2 x3 x4)
  (list x1 x2 x3 x4))

(define (foo2 x1 x2 #!optional x3 x4)
  (list x1 x2 x3 x4))

(define (foo2a x1 x2 #!optional (x3 -3) (x4 -4))
  (list x1 x2 x3 x4))

(define (test)
  (equal? '(1  2  -3  -4) (foo2a 1 2)))

(display (foo2a 1 2)) ;; --> (1 2 -3 -4)
(newline)
(display (test)) ;; --> #f
(newline)