If you don’t find an entry in the standard library that fits your needs, someone still may have written code that will be useful to you. Many superb library modules exist that are not included in the standard distribution, for various practical, political, and pathetic reasons. To find out what is available, you can look at the Comprehensive Perl Archive Network (CPAN). See the discussion of CPAN in Chapter 1.
Here are the major categories of modules available from CPAN:
Module listing format
Perl core modules, Perl language extensions, and documentation tools
Development support
Operating system interfaces
Networking, device control (modems), and interprocess communication
Data types and data type utilities
Database interfaces
User interfaces
Interfaces to or emulations of other programming languages
Filenames, filesystems, and file locking (see also filehandles)
String processing, language text processing, parsing, and searching
Option, argument, parameter, and configuration-file processing
Internationalization and locale
Authentication, security, and encryption
World Wide Web, HTML, HTTP, CGI, and MIME
Server and daemon utilities
Archiving, compression, and conversion
Images, pixmap and bitmap manipulation, drawing and graphing
Mail and Usenet news
Control-flow utilities (callbacks and exceptions)
Filehandle, directory handle, and input/output stream utilities
Microsoft Windows modules