The great thing about Open Source is you don't have to be invited to the party. Just start working and submit patches.

Some sources of ideas...

• The CPAN bug tracker. Pick a module you like. Pick a bug you want to fix. Work on it.
• The Perl bug tracker. With nearly 1500 open tickets there's always things to do even if that's just digging through old tickets and finding ones that have already been fixed.