There's a few different ways to track user
sessions, so you'll need to assess exactly which
one is best for your needs. This is covered by an
entire chapter in O'Reilly's Writing Apache Modules
in Perl and C. I'll recap a few of the methods that
don't absolutely require mod_perl.
Hidden tags - Each page is
generated via a script of some type. Store the
userid and such in hidden input tags of a form.
This method generally only works with a linear
flow of pages.
Cookies - This is probably
the quickest and easiest to implement based on
what you are asking for. Once they login, set a
session-based cookie (goes away when they close
their browser) that marks them as logged in. Of
course, if someone has cookies turned off, this
one isn't going to work.
Database - Store whether they
are currently logged in with a database. You have
to combine this with one of the above methods to
keep track of a session ID. You can also keep
track of the session ID in a query string on the
end of your URLs.