- do your script headers contain a correct cookie? >> How do i know that whether it is a correct cookie ?

You have to be a bit familiar with HTTP. If you are not, start reading a bit about it. There's lots of material out there on the internet. (I think this step is the most likely to work) <blockqoute> If so, is it also stored on disk? >> I am not aware about the location of cookies.

Then it's high time to become aware. You're storing stuff on your server, and don't know where? It's documented, you know. From CGI::Session::Driver::file:

If you wish to specify a session directory, use the Directory option, which denotes location of the directory where session ids are to be kept. If Directory is not set, defaults to whatever File::Spec->tmpdir() returns. So all the three lines in the SYNOPSIS section of this manual produce the same result on a UNIX machine.

And finally...

Does the browser send the cookie correctly back to the server? >> How do i know that ?

Wireshark. The user makes a request, the server responds and sets a session ID in the cookie. During the next request, the client should send the same session ID as the cookie. Check that.

I'm sorry to tell you that debugging persistence problems actually requires you to understand what's going on, which means you have to learn stuff about the underlying mechanisms.