A module is a collection of functions that is used in multiple programs. You would use a module in different ways, depending on the way it's implemented.

1. A class for an OO system
2. A repository of functions, with Exporter

CPAN is the Comprehensive Perl Archive Network. Among many other purposes, it serves as a repository for useful modules. Some of the ones you'll hear a lot about are CGI, Class::*, and Devel::*.

You would download a module from CPAN and install it, using the instructions that came with the module.

As for more info, I suggest purchasing Programming Perl, 3rd edition. There's a number of chapters there about modules and a whole chapter on CPAN.

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We are the carpenters and bricklayers of the Information Age.

Don't go borrowing trouble. For programmers, this means Worry only about what you need to implement.