Perl module: Difference between revisions

Revision as of 03:43, 31 May 2009

Revision as of 18:13, 12 June 2009

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A '''Perl module''' is a discrete component of software for the [[Perl]] programming language. Technically, it is a particular set of conventions for using Perl's [[#Perl packages and namespaces|package]] mechanism that has become universally adopted.{{discuss|Packages and modules}}

A module defines its source code to be in a '''[[package]]''', the Perl mechanism for defining [[namespaceNamespace (computer science)|namespaces]]s, e.g. ''CGI'' or ''Net::FTP'' or ''XML::Parser''; the file structure mirrors the namespace structure (e.g. the [[source code]] for ''Net::FTP'' is in ''Net/FTP.pm''). This mechanism is similar to that of [[Java package]]s. Furthermore, a module is the Perl equivalent of the [[class (computer science)|class]] when [[object-oriented programming]] is employed.{{discuss|Packages and modules}}

A collection of modules, with accompanying documentation, build scripts, and usually a test suite, compose a '''distribution'''. The Perl community has a sizable library of distributions available for search and download via [[CPAN]].

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==Perl packages and namespaces==

A running Perl program has a built-in [[Namespace (computer science)|namespace]] called "<code>main</code>", which is the default name. For example a subroutine called <code>Sub1</code> can be called as <code>Sub1()</code> or <code>main::Sub1()</code>. With a variable the appropriate sigil is placed in front of the namespace; so a scalar variable called <code>$var1</code> can also be referred to as <code>$main::var1</code>, or even <code>$::var1</code>. Other namespaces can be created at any time.

<source lang="perl">

package Namespace1;