s c h e m a t i c s : c o o k b o o k

(define (regexp-split-inclusive re str)
  (let ((unmatched-part (lambda (str next-match index)
                          (if (not next-match) 
                              (if (< index (string-length str))
                                  (list (substring str index))
                                  '())
                              (if (not (eq? index (caar next-match)))
                                  (list (substring str index (caar next-match)))
                                  '())))))
    (let loop ((parts '())
               (index 0)
               (next-match (regexp-match-positions re str)))
      (if (not next-match)
          (reverse (append (unmatched-part str next-match index) parts))
          (loop (cons (substring str (caar next-match) (cdar next-match))
                      (append (unmatched-part str next-match index) parts))
                (cdar next-match)
                (regexp-match-positions re str (cdar next-match)))))))

> (regexp-split-inclusive " +" "This is a     test")
("This" " " "is" " " "a" "     " "test")