There's a bug in your code: $cgi->cookie("SESSION_COOKIE") should be $cgi->cookie(SESSION_COOKIE) (SESSION_COOKIE is a constant - if you quote it, you'll end up with the string "SESSION_COOKIE" instead of the value of the constant).

As I've mentioned before, you don't need all that crufty code just to set up a session.

In other words, you probably don't get a persistent session at all. You have been working on this script for over a week now. Have you actually checked whether it does what you think it does?