gistfile1.el

(defun recursive-find-dirs(dir-name dir &optional working-dirs)
  "find all directories with the name DIR-NAME within DIR, recursively."
  (print working-dirs)
  (setq working-dirs (or working-dirs '()))
  (let ((dirs (directory-files-and-attributes dir t directory-files-no-dot-files-regexp)))
    (when dirs
      (dolist (current-dir dirs)
        (when (file-directory-p (car current-dir))
          (if (string-equal (car (last (split-string (car current-dir) "/"))) dir-name)
              (push (car current-dir) working-dirs))
          (recursive-find-dirs dir-name (car current-dir) working-dirs)))))
    working-dirs)

;; print shows that it always (at some point) has all of the directories found correctly,
;; however one or more somehow get removed. also it always RETURNS nil.