Perl module: Difference between revisions

Revision as of 12:41, 30 December 2004

Revision as of 04:54, 17 January 2005

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A '''Perl module''' is a discrete component of software for the [[Perl]] programming language. A module is distinguished by a unique namespace, e.g. "CGI" or "Net::FTP" or "XML::Parser". By conventions, there is typically one module per file with a .pm extension. A collection of one or more modules, with accompanying documentation and build scripts, compose a package. The Perl community has a sizable library of packages available for search and download via [[CPAN]].

It is common for Perl modules to have embedded documentation in Perl's [[Plain Old
Documentation|POD]] format. Many modules favor an [[object-oriented]] style, but many are [[procedural]] instead, especially old modules.

Below is an example of a very simple object-oriented Perl module and a short program which makes use of the module. It is implemented in a dialect of Perl5 which is compatible with Perl 5.6.0 and higher.

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''Hello/World.pm''

----

# The 'package' command gives the name of the module or class.

package Hello::World;

use strict;

use warnings;

# By convention, a module's version number is stored in

# $ModuleName::VERSION; certain forms of the "use" built-in depend

# on this variable being defined.

our $VERSION = "1.0";

# Lines starting with an equal sign indicate embedded POD

# documentation. POD sections end with an =cut directive, and can

# be intermixed almost freely with normal code.

=head1 NAME

Hello::World - An encapsulation of a commonly output message

=head1 SYNOPSIS

use Hello::World;

my $hw = new Hello::World();

$hw->print();

=head1 DESCRIPTION

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message.

=head1 SYNOPSIS

Use like this:

use Hello:World;

my $hw = new Hello:World();

$hw->print();

=head1 METHODS

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}

=item toStringto_string

Returns the greeting as a string

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=cut

sub toStringto_string {

my $self = shift;

return $self->{message};

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=head1 AUTHOR

Joe Hacker <[e-mail]>

=cut

# The lone "1;" at the end of the file indicates that the module

# has been successfully initialized. Some modules contain code

# that runs as soon as the module is compiled, before the program

# that included it is finished compiling; they can arrange to return

# a non-true value if something goes wrong.

1;

----