Editing CPAN (section)

==CPAN.pm, CPANPLUS, and cpanminus==
There is also a Perl core module named CPAN; it is usually differentiated from the repository itself by using the name CPAN.pm. CPAN.pm is mainly an interactive shell which can be used to search for, download, and install distributions. An interactive shell called {{mono|cpan}} is also provided in the Perl core, and is the usual way of running CPAN.pm. After a short configuration process and mirror selection, it uses tools available on the user's computer to automatically download, unpack, compile, test, and install modules. It can also self-update.

An effort to replace CPAN.pm with something cleaner and more modern resulted in the CPANPLUS (or CPAN++) set of modules. CPANPLUS separates the back-end work of downloading, compiling, and installing modules from the interactive shell used to issue commands. It supports several advanced features, such as cryptographic signature checking, test result reporting, and uninstalling a distribution. CPANPLUS was added to the Perl core in version 5.10.0, and removed from it in version 5.20.0.

A smaller, leaner modern alternative to these CPAN installers was developed called cpanminus. cpanminus was designed to have a much smaller memory footprint as often required in limited memory environments, and to be usable as a standalone script such that it can even install itself, requiring only the expected set of core Perl modules to be available. It is also available from CPAN as the module App::cpanminus, which installs the {{mono|cpanm}} script. It does not maintain or rely on a persistent configuration, but is configured only by the environment and command-line options. cpanminus does not have an interactive shell component. It recognizes the cpanfile format for specifying prerequisites, useful in ad-hoc Perl projects that may not be designed for CPAN installation. cpanminus also has the ability to uninstall distributions.

Each of these modules can check a distribution's [[Coupling (computer programming)|dependencies]] and recursively install any prerequisites, either automatically or with individual user approval. Each support FTP and HTTP and can work through firewalls and proxies.