If you are just getting and installing one or a few modules, it’s not a big problem to download the module’s tarball and run through the build process manually. But if you don’t want to cope with the brute-force approach when dealing with large module installations (such as LWP and the CPAN bundle), there is an easier way—you can use the CPAN module. The CPAN module (CPAN.pm) can be used interactively from the command line to locate, download, and install Perl modules and their dependencies, or to identify modules and authors. CPAN.pm was designed to automate the installation of Perl modules; it includes searching capabilities and the ability to retrieve files from one or more of the mirrored CPAN sites and unpack them in a dedicated directory.

To run the CPAN module interactively, enter:

% perl -MCPAN -e shell

The first time you use the CPAN module, it takes you through a series of setup questions and writes CPAN::Config if you run the above as root or your administrative user. If the above is run as a user who does not have administrative permissions, CPAN.pm determines who you are and writes MyConfig.pm in a subdirectory of your home directory (defaults to ~/.cpan/CPAN/MyConfig.pm). After that, whenever you use the CPAN module for downloading other modules, it uses the .cpan directory as the general build and cache directory, saved as cpan_home in the configuration file. If ReadLine support is available (i.e., Term::ReadKey and Term::ReadLine are installed), you can use command history and command completion as you enter commands.

When the module runs and is ready for commands to be entered, you’ll see the prompt:

cpan>

You can then enter h to get a brief help message, or just start entering commands. The commands are all methods in the CPAN::Shell package. For commands that can operate on modules, bundles, authors, or distributions, CPAN.pm treats arguments containing a slash (/ ) as distributions, arguments beginning with Bundle:: as bundles, and everything else as modules or authors. The following is a listing of the interactive CPAN commands.