Apache SpamAssassin is an extensible email filter that is used to identify spam. Once identified, the mail can then be optionally tagged as spam for later filtering. It provides a command line tool to perform filtering, a client-server system to filter large volumes of mail, and Mail::SpamAssassin, a set of Perl modules allowing Apache SpamAssassin to be used in a wide variety of email systems.
metaf2xml can download, parse, and decode aviation routine weather reports (METAR, SPECI, SAO), aerodrome forecasts (TAF), synoptic observations (SYNOP), and BUOY observations, and store the data as XML. XSLT style sheets convert it to plain language, as HTML or text. Current weather data from NOAA and other sources can be fetched and displayed.
Config-Model provides a framework for editing and validating the content of any configuration file or data. With a configuration model (expressed in a data structure), Config-Model provides a user interface and a tool to validate configuration. An optional graphical (Perl/Tk) or curses interface can be used to edit configuration data that will be validated according to the user-provided model. Config-Model includes a model example for fstab and a small fstab demo.
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.
qpsmtpd is a flexible smtpd daemon written in Perl. Apart from the core SMTP features, all functionality is implemented in small "extension plugins" using the easy-to-use object oriented plugin API. qpsmtpd was originally written as a drop-in qmail-smtpd replacement, but now it also includes an smtp forward and a postfix "backend".
Zoidberg (a.k.a. zoid) provides a modular Perl shell written, configured, and operated entirely in Perl. It aspires to be a fully operational login shell with all the features one normally expects. But it also gives direct access to Perl objects and data structures from the command line, and allows you to run Perl code within the scope of your command line.