DBIx-Class is an SQL to OO mapper with an object API inspired by Class::DBI (with a compatibility layer as a springboard for porting) and a resultset API that allows abstract encapsulation of database operations. It aims to make representing queries in your code as Perl-ish as possible while still providing access to as many of the capabilities of the database as possible, including retrieving related records from multiple tables in a single query.
Job-Machine is a small, but versatile system for sending jobs to a message queue and, if necessary, communicating answers back to the sender. Job::Machine uses LISTEN / NOTIFY from PostgreSQL to send signals between clients and workers. This ensures very efficient message passing, giving any worker that is awake the chance to start working immediately.
Libev is a high-performance event loop for C (with optional and separate interfaces for C++ and Perl), featuring support for I/O, timers (relative and absolute, cron-like ones), signals, process status changes, and other types of events. It has both a fast native API and libevent emulation to support programs written using the libevent API. Differences to libevent include higher speed, simpler design, more features, less memory usage, embedability, and no arbitrary limits. libev supports epoll, kqueue, Solaris event ports, poll, and select.
Geo::METAR is a Perl module for parsing METAR data (aviation weather reports). You can retrieve weather data from airports around the world. and get the current temperature, cloud coverage, and so on. Included in the distribution is a sample Perl script that uses LWP to fetch current data from the airport of your choice and spits out the current temperature.
Plack is a set of tools for using the PSGI stack. It contains middleware components, a reference server, and utilities for Web application frameworks. PSGI allows Web application framework developers to only write an adapter for PSGI. End users can choose from among all the backends that support the PSGI interface: CGI, FastCGI, mod_perl, the Nginx perl module, and standalone servers.