Get the userid from where? From the user, or from the session? Basic sessioning goes like this:

1. A user connects to your CGI, you check if there is a sessionid parameter, if not, you create them a new session.
2. Either you provide them a form to enter a userid in, or you assign them one, you put that data in the session (from the cgi parameter of the form, or using the userid you made up)
3. The user visits another page, you notice they have a sessionid parameter, you use that id to create a CGI::Session object, and read the userid from that object

So, where is the problem exactly?

C.