Catalyst - "The elegant MVC framework". Designed with flexibility in mind, it lets the user choose among a variety of storage models, templating systems, web servers, and operating systems. - http://www.catalystframework.org/
Jifty - A way to build web applications based on the DRY ("don't repeat yourself") principle. - http://jifty.org/
Maypole - Perl framework for MVC-oriented web applications, designed to minimize coding requirements for creating simple web interfaces to databases, while remaining flexible enough to support enterprise web applications. - http://maypole.perl.org/
Mason HQ - Mason is a Perl-based web programming language. Among other things, it allows Perl to be embedded in HTML. - http://www.masonhq.com/
Web Client Programming with Perl - Full text of the out-of-print book by Clinton Wong. - http://www.oreilly.com/openbook/webclient/
Perl for the Web - On-line (and print) book by Chris Radcliff about creating fast dynamic Web sites with Perl. - http://www.globalspin.com/thebook/