;;; submitted by Friedrich Dominicus, added by the invisible hand
  ;;; do all sorts of things to files (file names) in a directory 

  (define (operate-on dir action transformer pattern)
    (with-cwd dir
      (for-each (lambda (file)
                  (action file (transformer file)))
                (glob pattern))))

  ;; e.g.
  (define (upcase-file-names dir pattern)
    (operate-on dir rename-file string-upcase pattern))