Perl: How to Write a Module

By Xah Lee. Date: . Last updated: .

Here's to write a module in Perl by a example.

Save the following 3 lines in a file and name it mymodule.pm.

# -*- coding: utf-8 -*-
# perl

package mymodule;  # declaring the module

sub f1($){$_[0]+1}  # module body

# more code here

1   # module must return a true value

Then, call it like the following way:

# -*- coding: utf-8 -*-
# perl

use mymodule;  # import the module
print mymodule::f1(5);   # call the function

This is the simplest illustration of writing a package in Perl and calling its function.

Module vs Package

The word “module” and “package” are often used interchangably. Sometimes in a technical context, the word “module” refers to a file, and the word “package” refers to the namespace.

Module File Path Correspondence

Module/package name corresponds to the file's name/path. For example, if you have a module at

abc.pm

you load it like this:

use abc;

module file can be grouped into directories. If you have a module with subdirs, named:

GameX/sound.pm

you can load it like this

use GameX::sound;

The double colon :: corresponds to directory separator /.

Perl Module/Package

Perl

Detail

String

Boolean

Conditional

Data Structure

Loop, Iteration

Function

Text Processing

Advanced

misc