Perl module

A Perl module is a discrete component of software for the .

It is common for Perl modules to have embedded documentation in Perl s Plain Old Documentation 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.

helloworld.pl

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#!/usr/bin/perl -w use Hello::World; my $hello = Hello::World->new(); $hello->print();

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Hello/World.pm

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# 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 This is an object-oriented library which can print the famous H.W. message. =head1 METHODS =over =item new Instantiates an object which holds a greeting message. =cut sub new { my $pkg = shift; my $self = bless({ message => Hello, world! , }, $pkg); return $self; } =item to_string Returns the greeting as a string =cut sub to_string { my $self = shift; return $self->{message}; } =item print Outputs the greeting to STDOUT =cut sub print { my $self = shift; print $self->toString(), ; } =back =head1 AUTHOR Joe Hacker =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;

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