"is a support module for CGI scripts. It manages a tree of data, so that the script can display the tree, and the user can click on a node in the tree to open or close that node." This, in combination with mod_perl, would be a useful tool for groups who write and share OPML documents ( any XML document really ) to a fileshare/webdav folder but don't want to serve them via the web using a Frontier, or whatever it's called this week, server.