WebTools is "system" of multiple modules and libraries. Along with template engine capabilities, it features session management, global variables support, cookies support, and various database interfaces. It also features a pure Perl mail client, categories management, form checking, and libraries such as a CGI-based downloading library, HTML parsers, and a library that makes PHP functions available to Perl for ease of development.
Search::Xapian is a Perl XS frontend to the Xapian C++ search library. It is a fairly complete wrapper: most features of the Xapian library are made available for use from Perl. Xapian is a highly adaptable toolkit that allows developers to easily add advanced indexing and search facilities to their own applications. It supports the Probabilistic Information Retrieval model as well as a rich set of boolean query operators. It's fast and scalable to hundreds of millions of documents.
txt2html is a Perl program that uses the HTML::TextToHTML perl module to convert plain text to HTML. It supports headings, lists, tables, simple character markup, hyperlinking and is highly customizable. It recognizes some of the apparent structure of the source document (mostly whitespace and typographic layout) and attempts to mark that structure explicitly using HTML.
HTML::Mason is a full-featured web site development and delivery system. Mason allows web pages and sites to be constructed from shared, reusable building blocks called components. Components contain a mix of Perl and HTML, and can call each other and pass values back and forth like subroutines. Components increase modularity and eliminate repetitive work. HTML::Mason is most powerful when used in conjunction with mod_perl, but can be used in standalone applications as well.
OpenGuides is a wiki-like package for maintaining a collaborative city guide. It is written in Perl and runs as a CGI program, and uses either the MySQL, PostgreSQL, or SQLite database. It offers features over a "normal" wiki such as metadata management and a "find nearby things" function. The look and feel is highly customizable thanks to use of the Template Toolkit.