Task - The successor to Bundle:: for installing sets of modules


  ### In Makefile.PL
  use inc::Module::Install;
  name         'Task-Foo';
  abstract     'Install the most common Foo modules';
  author       'Adam Kennedy <>';
  version_from 'lib/Task/';
  license      'perl';
  # All the things we need for Foo
  requires     'perl'           => '5.005';
  requires     'Carp'           => 0;
  requires     'File::Basename' => 0;
  requires     'Storable'       => 0;
  requires     'Params::Util'   => '0.06';
  ### In lib/Task/
  package Task::Foo;
  use strict;
  use vars qw{$VERSION};
      $VERSION = '1.00';


The Bundle:: namespace has long served as the CPAN's "expansion" mechanism for module installation. A Bundle:: module contains no code in itself, but serves as a way to specify an entire collection of modules/version pairs to be installed.

The Problem with Bundle::

Although it has done a reasonably good job, Bundle:: modules suffer from some problems.

Firstly, Bundle:: functionality is fairly magical. The Bundle:: magic needs to be specially implemented by the CPAN client, and a Bundle:: dist is treated differently to every other type of dist.

It provides only static dependencies. That is, it only provides a specific set of dependencies, and you cannot change the list depending on the platform (for example, installing an extra Win32:: module if the bundle is being installed on Windows).

Finally, it exists only in CPAN. It is not possible to take a Bundle:: dist and just install it, because Makefile.PL files are irrelevant for Bundle:: dists.

The irony now is that an ordinary module has far more flexible and powerful dependency capabilities than Bundle:: distributions. And because the functionality is hard-coded into the CPAN clients for the entire Bundle:: namespace, moving beyond the current situation is going to mean a change of namespace.

Requirements for a Bundle:: Successor

The Task:: namespace (modeled off the Debian packages of the same name) is used to provide similar functionality to the traditional Bundle:: namespace, but without the need to magic and special client-side support in order to have them work.

A Task:: module is implemented as a normal .pm module, with only a version defined. That .pm module itself should NOT load in all the dependencies.

This implementation as a module allows normal Perl tools to be able to load the module and check it's version to confirm you have the required modules, without the need for a CPAN client involved.

Instead of using a magic POD format, the dependency specification is implemented using the Makefile.PL, as you would for any other module.

This also means that if the Task needs to check for the existence of a non-Perl application, or some other dependency, it can be done as well.

And you can adapt the dependencies based on the configuration of the system.

For example, if a module is upgraded to repair a critical bug that applies only for Windows platform, you can use two alternate versions based on platform detection code, rather than needing to apply the highest version in all cases.

This "normal" implementation also means that Bundle:: modules can be created privately and no longer need to be stored in CPAN, opening up the bundling capability to companies and other non-public users.

You should also be able to do things like encode the full dependencies for you web application as a private Task:: dist and send this tarball to the hosting company.

Their admin can then use the dist to install the required modules from CPAN and you can be far more certain that the required modules have been installed than in the traditional case.


At this time the preferred implementation is done using Module::Install.

Module::Install allows a much more simplified syntax, and bundles the required "Do What I Mean" functionality in the distribution itself.

This bundling removes many assumptions on what may or may not be installed on the the destination system, as the installation logic can be included in the dist and does not have to be first fetched from CPAN.

It also provides you with the additional functionality from the family of Module::Install extension classes. See the Module::Install page for more details.

Of course, this is merely a convention. If you wish to write your Makefile.PL/Build.PL file using another installer, you are free to do so.

Please note that this Task class provides no functionality in and of itself, and your Task:: distributions do not need to inherit from it.

In general, you also should not need to provide any test scripts for your Task:: distribution, although you may wish to add tests to validate the correct installation if you wish (another option not available in Bundle:: distributions).


Bugs (or really, spelling mistakes) should be reported via the CPAN bug tracker at

For other issues, contact the author.


Adam Kennedy <>


Copyright 2005 - 2008 Adam Kennedy.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

The full text of the license can be found in the LICENSE file included with this module.