PEAR::Tree walk function usage

Hi Wolfram, I have a tree with chapters and subchapters (and subchapters ...) Now I want to modify some values in that tree and I thought that the walk function could do the trick, but I can't get it right. I want to do the following (these are just example trees): Convert: Chapter on Horses -- subchapter -- subchapter ------sub sub chapter ------sub sub chapter Chapter on Camels -- subchapter -- subchapter ------sub sub chapter ------sub sub chapter Into: 1.Chapter on Horses -- 1.1subchapter -- 1.2subchapter ------ 1.2.1sub sub chapter ------ 1.2.2sub sub chapter 2. Chapter on Camels -- 2.1subchapter ------2.1.1.sub sub chapter ------2.1.2sub sub chapter -- 2.2subchapter ------2.2.1sub sub chapter ------2.2.2sub sub chapter I know there are some clever functions (like the walk one) hiding away in your class. Could you point me in the right direction? Thanks Jeroen