Dear forum,

if I set doxymacs-doxygen-dirs as suggested in the documentation, i.e.

(defcustom doxymacs-doxygen-dirs
  "List associating pathnames with Doxygen documentation.
  :type 'list
  :group 'doxymacs)

and try to look up the documentation via C-c d ?, I get the message
Wrong type argument: stringp, \"^/home/me/project/foo/\"
even if the path exists.

What is wrong here and how can I fix it?
I use GNU emacs 21.3.1.