(module
 foo
 (bar)
 (import scheme chicken)

 (define (bar . args)
   (let ((foobar '()))
     (do ((rest args (cddr rest)))
	 ((null? rest)
	  (if (null? foobar)
	      'gaga
	      foobar))
       (if (null? (cdr rest))
	   (error (car rest)))
       (case (car rest)
	 ((#:foobar)
	  (set! foobar (cons (cadr rest) foobar)))))))

)

(import foo)

(display (bar #:foobar 42))
(newline)