The CPAN

Author: John M. Gabriele | back to index

  • The CPAN

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    Overview

    There's a Perl standard libary module called CPAN. It's actually been superceded as of late by the CPANPLUS module.

    There is also the Comprehensive Perl Archive Network, aka, The CPAN. When users speak of this, they sometimes refer to it as "the CPAN" to distinguish it from the module of the same name. Another option is to write the CPAN module as "CPAN.pm".

    The CPAN is vast. Sam Tregar has noted:

    "CPAN is my programming language of choice, the rest is just syntax."

    Due to its size, scope, maturity, and ease of use, you'll find that there is very often a module in the CPAN to help you with whatever problem you happen to be working on.

    Terminology

    A few terms relating to things found in the CPAN:

    Module

    A regular Perl module (a file that ends in ".pm")

    Distribution

    When one or more modules are tar.gz'd up together with the accompanying README, Build.PL (or Makefile.PL), tests, etc. -- that's a distribution.

    Distribution file

    The .tar.gz file that a given distribution is packed into. The name of the distribution file does not necessarily have to correspond to the module or modules it contains, but usually does.

    Chapter or Category

    When an author uploads a distribution to CPAN, they may choose a chapterid to associate with the distribution. That group of categories that are listed at search.cpan.org are all the chapters that the CPAN knows about. That same list shows up when you look at modules on CPAN by-category.

    Package

    A namespaces where the names in a given module live. You declare the package name at the top of your module, with a line that looks like package Foo::Bar;.

    Register Namespace

    This is something a module/distribution author does after they upload their distribution file to CPAN. It's for registering the module in the module list. This way, the module shows up in the "by-module" and "by-category" listings on CPAN.

    Bundle

    CPANPLUS knows about "Bundles". As the CPAN docs describe, Bundles are just modules that list their dependencies in a simple but crude way so that CPANPLUS can understand. If you install the bundle, you get all its listed dependencies too. It makes installing larger collections of related modules easier, but Bundles have now been superceded by Tasks.

    Task

    Successor to Bundle. Rather than using the magic convention for naming dependencies like Bundle does, Tasks put the dependencies right into a Build.PL file (or makefile) so CPANPLUS handles them just like other modules. See the docs for the Task module on CPAN. Don't use Bundles anymore -- use Tasks instead.

    Dependencies / Prerequisites

    Dependencies for a distribution (modules that the distribution needs to be already installed) get specified in the Build.PL (or Makefile.PL) file. CPANPLUS can determine what module distributions it needs to install to fulfill these prerequisites.

    Module and Distribution names

    It's most common for a distribution to contain one main module, possibly with one or more sub-modules. If the main module is Foo::Bar, the distribution file is typically named "Foo-Bar-n.m.o.tar.gz", where n, m, and o represent revision, version, and subversion numbers, respectively.

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