POP3 Forwarding help needed

I remember doing something like this in the past and was wondering if anyone
had any suggestions.

Scenario: I am hosting several email accounts with an ISP (access via
POP3/Outlook). I want to move to another ISP. I have all of the usernames
and passwords.

Goal: is to move the unread mail (mail on the old ISP) to the new isp for
each user.

The way I did it before was a PERL script the cycled through the usernames
SU as the user and POPped the mail down. This works great to get it to the
server, but now I need to forward each to a different ISP/User.

Anyone have any ideas/scripts/software?

Thanks,
Dave