The Perl You Need to Know Part 23: CPAN, a Farmer's Market for Perl - Page 164

Summer in the country means "u-pick" time, when you pull the car off onto dusty gravel roads, grab some pecks, bushels, pints, buckets, or flats, and load up on fresh-from-the- fields goodness. But no matter how large and varied your favorite farm may be, it's still just one farm. Come Saturdays, or Sundays, or Tuesdays, the farmer probably loads up his old truck and chugs it down to the farmer's market, because he knows that's where all the shoppers are at. And the shoppers know that's where the farmers are at. The power of centralized distribution benefits both seller and buyer, and the popularity of outdoor markets — be they farmers, fleas, or even indoor malls — stand as a testament to centralization. It's often said that in Perl community is one of its greatest assets, and a major reason for that is CPAN — the Comprehensive Perl Archive Network. A farmer's market, if you will, especially if you're hunting for Perl modules.

Come One, Come All

Because extending the power of Perl is as straightforward as packaging your tool into a Perl module, authors from around the world have been furiously hatching modules for years. Indeed, some modules have become so significant to Perl that they've been adopted into the "standard distribution" — the set of modules that is included by default with a particular version of Perl. Beyond this core of standard modules orbits hundreds of mercenary modules, lying in wait to help you if you need them.

Without CPAN, locating a Perl module that suits your needs would be like driving from farm to farm until you found the one that grew cucumbers. One stop shopping at its finest, CPAN, in a general sense, maintains a sophisticated collection of Perl modules spanning many categories. More precisely, though, CPAN itself is a Perl module — put another way, there is a Perl module named CPAN with which you can browse and install modules from the archives.

The Unprivileged User

Quite a lot of Perl documentation and conversation implicitly assumes that you have access and control over the Perl installation on a particular machine. Indeed, such access makes life easier in some respects, and it's not unfair to suggest that many people use Perl on home machines and other systems for which they wield total control. But as Perl's popularity as a Web authoring language has grown, many newcomers to Perl find themselves using systems hosted by others — quite often, their hosting service or other type of service provider.

In some cases, hosted users might be able to create a fresh Perl installation inside their own user account. This may be desirable, or it may not. It may be allowable, or it may not. For the purposes of this argument, we'll assume the least privileged scenario: users who cannot install a full Perl distribution inside their account, and who cannot control or request that new modules be added to the hosted Perl distribution. Anyone with greater privileges than these should have no problem adapting the CPAN concepts herein to their own systems. We are also assuming a Unix-derived operating system, such as Linux — those who author Perl on, say, a Windows machine using ActiveState Perl will not use CPAN, but rather ActiveState's own module management system called ppm.

Contents:

A Dark And Stormy Night ...
Inside CPAN
They Shoot Coders, Don't They?
A Private Stash (of modules)

A Toolbox Heritage - Page 163
The Perl You Need to Know
A Dark And Stormy Night ... - Page 165