There is Dada Mail which is a simple CGI (non mod_perl or FastCGI) mailing list manager written in Perl. I've used it for a couple of clients with very specific needs which it met, but overall I'm much more impressed with Mailman.
This Freshmeat search for 'mailing list perl' turns up a few projects.
Probably a decade ago I wrote a multiple-list package from scratch in Perl for my employer at the time who wanted some very particular features. Those included having the hosting company set up accounts for clients and assigning each client a maximum number of lists and a maximum number of overall subscribers, allowing the the clients to have lists open or closed and outbound-only or repeating inbound mail possibly from members only, figuring the cost basis for the hosting company of each list to adjust subscription pricing, and allowing the hosting company to override administration of a list when necessary. I'm sure the code's a mess if it even still exists. I could try to find it if anyone wants to look into breathing life into it. I'm not interested in the code personally, at least not for free. I'd be happy to put it out there for someone else to clean up if I can find it and get permission, though.
Overall, I'd use what works, even if it's not in Perl. If I have to do much customization, I'd prefer Perl over most other languages just because of my preference for Perl.