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Perl modules

Perl module is a package within a file which uses its own namespace. It's a collection of subroutines and variables,  Some subroutines can be "exposed" - visible in the namespace into which you incorporate the module. Technically, it is a particular set of conventions for using Perl's package mechanism that has become universally adopted. for example exporting subroutines into the namespace of the invoking script via @EXPORT mechanism provides by exporter

A Module is a collection of related subroutines and data designed to be used by other programs or modules. Modules are defined in separate files and use the package keyword to define a namespace for the data and subroutines in that module file.

A Module can be a simple collection of subroutines, not defining a class. Such modules are referred to as libraries.

A Class is a user-defined data type. Classes are defined in modules using special constructs that allow you to create variables of that type. The subroutines in these modules are referred to as methods.

An Object is a variable that belongs to a particular class. It contains its own, private data that can be operated on by the methods defined in the class. The object is called an instance of its class.

Example:

• Module: Person.pm
• Class: Person
• Object: "Lincoln Stein"
• Method: surname()

What's up with all the double colons (::)? The :: corresponds to a filesystem path separator. A Module called Shape::Rect corresponds to a file named Shape/Rect.pm relative to a module library directory. 

Perl comes with a large library of modules. In recent version it is essentially too big to be useful.  But you can be selective.

As modules use their own namespace they cannot conflict with variable in your code and thus they enhance code reuse.

A huge archive of Perl modules CPAN (Comprehensive Perl Archive Network) was collected over the time.

Recommended Links

Perl module - Wikipedia, the free encyclopedia

Perl Module Mechanics by Steven McDougall  2007 March 02

This page describes the mechanics of creating, compiling, releasing and maintaining Perl modules.

This is not a reference manual. Rather, it is a running account of how to do these things. More to the point, it is an account of how I do these things. Accordingly

• It ignores XS
• Pathnames and other details may vary on your system
• You have to put up with a certain amount of editorializing

See also Perl Module Anatomy  by Steven McDougall. Short and not very informative notes about the contents of the .pm file

The very very short tutorial about modules in Perl [ New: 06/16/99 ]Mark-Jason Dominus a really short tutorial about Perl Modules.

The Seven Useful Uses of local

perltoot - Tom Christiansen's object-oriented tutorial for perl

IBM developerWorks: Parsing with Perl modules(Apr 30, 2000)

modules

Perl Module Primer By Dan Ragle

Perl module - Wikipedia, the free encyclopedia

• Perl modules (packages and symbol tables)
• Constructing new Perl modules and finding existing ones
• Perl module style guide
• Preparing a new module for distribution
• CPAN

Installing Your Own Perl Modules

Creating (and Maintaining) Perl Modules

Amazon.com- Perl Modules- Eric Foster-Johnson- Books

Perl Module Review- Class--Trait - O'Reilly ONLamp Blog

O'Reilly Perl Center

Writing Apache Modules with Perl and C - by Lincoln D Stein - 744 pages
Learning Perl Objects References and Modules - by Randal L Schwartz - 228 pages

Reference

Websites:

genome-www.stanford.edu/perlOOP	A little collection I put together as I was learning Object-oriented Perl programming. See especially the examples page.
www.perl.com/CPAN/CPAN.html	CPAN homepage
search.cpan.org	Search CPAN for a module by author, category, or module name
bioperl.org	The Bioperl project - modules for bioinformatics