(define (expand-symbol x)
  (let loop ((s (symbol->string x)))
       (let ((i (string-rindex s #\.)))
         (if i
             `(assoc-ref ,(loop (substring s 0 i))
                         (quote ,(string->symbol (substring s (1+ i)))))
           (string->symbol s)))))

(define (expand-dot! x)
  (cond ((symbol? x) (expand-symbol x))
	 ((pair? x)
          (cond ((eq? (car x) 'quote) x)
                (else
                 (set-car! x (expand-dot! (car x)))
                 (set-cdr! x (expand-dot! (cdr x)))
                 x)))
         (else x)))

(use-syntax expand-dot!)