I hope i understand your network setup correctly (i had to fill in a few blanks with sane defaults).

Probably the easiest solution would be to write a batch script on one of the windows boxes that runs the the CPAN-Mini update (mcpani --update) and then "rsync -e ssh..." to on of the unix boxes.

If the Perl installation on the Windows box is configured correctly (Proxy settings in ENV http_proxy and whatnot) and you install rsync for Windows, this should pretty much work. After verifying, you could add that to the planned tasks, so it runs every day/wee/month automatically.

What i don't understand is this: How do you install security updates and such on your Unix boxes if they can't download from the internet? Manually?? That sounds like a security problem in itself...