Most Perl modules are written in Perl, some use XS (they are written in C) so require a C compiler (it's easy to get this setup - don't panic), see your OS of choice below to find out how to get the right compiler. Modules may have dependencies on other modules (almost always on CPAN) and cannot be installed without them (or without a specific version of them). It is worth throughly reading the documentation for the options below. Many modules on CPAN now require a recent version of Perl (version 5.8 or above).