CHAPTER 7

Great CPAN Modules

CPAN 

HOUSES A WIDE VARIETY

 of modules, from 10 line modules created by a 

single author to massive 10,000 line multifile modules created by teams of pro 

grammers. In fact, size and complexity are just one measure of variety in CPAN 

modules. Along every conceivable axis design, documentation, implemen 

tation, testing, packaging there exists great variety. CPAN is a virtual jungle 

teeming with biodiversity.

And, like a real jungle, CPAN hosts a struggle for survival. Modules on CPAN 

don't compete for food and shelter, but they do compete for equally scarce resources: 

users and developers. Open source projects depend on users to grow and evolve. 

Without a group of users and at least one dedicated developer, even the best 

module on CPAN will soon find itself growing obsolete.

Of course, failure in this struggle isn't quite as perilous as it is in the real world; 

modules that fail to find a user community are never killed.

1

 Also, it must be 

stressed that although modules are pitted in competition, their authors are not. 

Nearly every CPAN author has a couple duds in their module directories, but that 

doesn't detract from the success of their better works.

This chapter will examine the properties of a  great  CPAN module by exam 

ining particularly successful modules. These modules have attracted large numbers of 

users and are often supported by a number of programmers. Since CPAN doesn't 

collect statistics on module usage,

2

 I've chosen modules to look at based on my 

own experience as a CPAN user. There are, of course, many excellent modules that 

I didn't have the time to include.

One of the best ways to learn how to create great CPAN modules is to read 

other great modules. Consider this chapter an annotated reading list and you'll be 

well on your way.

What Makes a Great CPAN Module?

The essential question of this chapter seems simple. So simple, in fact, that there's 

a single answer poised on the tip of every CPAN author's tongue: Great modules 

come from addressing a common problem in a reliable and efficient way.

1. Although some people think they should be! As Lincoln Stein, author of the CGI and GD 

modules, put it when asked what changes he would like to see in CPAN,  Purge the cruft! 

2. See the CPAN FAQ for an answer to the question,  Why not? 

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