Well, the idea was to allow those users with access rights to the forum to see it in the list while hiding it from those w/o access. Just a simple cookie and access rights check before rendering the forums list would seem to be what I need, but I am only just getting a grip on Perl and can't do it myself.
While your idea would work it would require distributing the "secret URL" to all users of the private forum and would eliminate entry into the forum via navigation by hyperlink.
