There is Apache::AuthCookie, which sounds quite similar to what you're doing. It's tied into mod_perl, though. I've been dieing to see a non-mod_perl solution (since my current employer has a wicked combination of legacy CGIs and political issues that keep us from using mod_perl).

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I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident.
-- Schemer

Note: All code is untested, unless otherwise stated