Web::Machine - A Perl port of Webmachine


version 0.17


  use strict;
  use warnings;

  use Web::Machine;

      package HelloWorld::Resource;
      use strict;
      use warnings;

      use parent 'Web::Machine::Resource';

      sub content_types_provided { [{ 'text/html' => 'to_html' }] }

      sub to_html {
                  <title>Hello World Resource</title>
                  <h1>Hello World</h1>

  Web::Machine->new( resource => 'HelloWorld::Resource' )->to_app;


Web::Machine provides a RESTful web framework modeled as a state machine. You define one or more resource classes. Each resource represents a single RESTful URI end point, such as a user, an email, etc. The resource class can also be the target for POST requests to create a new user, email, etc.

Each resource is a state machine, and each request for a resource is handled by running the request through that state machine.

Web::Machine is built on top of Plack, but it handles the full request and response cycle.

See Web::Machine::Manual for more details on using Web::Machine in general, and how Web::Machine and Plack interact.

This is a port of Webmachine, actually it is much closer to the Ruby version, with a little bit of the JavaScript version and even some of the Python version thrown in for good measure.

You can learn a bit about Web::Machine's history from the slides for my 2012 YAPC::NA talk.

To learn more about Webmachine, take a look at the links in the SEE ALSO section.


NOTE: This module is a Plack::Component subclass and so follows the interface set forward by that module.

new( resource => $resource_classname, ?resource_args => $arg_list, ?tracing => 1|0, ?streaming => 1|0, ?request_class => $request_class )

The constructor expects to get a $resource_classname, which it will use to load and create an instance of the resource class. If that class requires any additional arguments, they can be specified with the resource_args parameter. The contents of the resource_args parameter will be made available to the init() method of Web::Machine::Resource.

The new method can also take an optional tracing parameter which it will pass on to Web::Machine::FSM and an optional streaming parameter, which if true will run the request in a PSGI streaming response. This can be useful if you need to run your content generation asynchronously.

The optional request_class parameter accepts the name of a module that will be used as the request object. The module must be a class that inherits from Plack::Request. Use this if you have a subclass of Plack::Request that you would like to use in your Web::Machine::Resource.

inflate_request( $env )

This takes a raw PSGI $env and inflates it into a Plack::Request instance. By default this also uses HTTP::Headers::ActionPack to inflate the headers of the request to be complex objects.


This will create the Web::Machine::FSM object to run. It will get passed the value of the tracing constructor parameter.

create_resource( $request )

This will create the Web::Machine::Resource instance using the class specified in the resource constructor parameter. It will pass in the $request object and call new_response on the $request object to get a Plack::Response instance.

finalize_response( $response )

Given a $response which is a Plack::Response object, this will finalize it and return a raw PSGI response.

call( $env )

This is the call method overridden from the Plack::Component superclass.


If you set the WM_DEBUG environment variable to 1 we will print out information about the path taken through the state machine to STDERR.

If you set WM_DEBUG to diag then debugging information will be printed using Test::More's diag() sub instead.


The diagram -
Original Erlang -
Ruby port -
Node JS port -
Python port -
2012 YAPC::NA slides -
an elaborate machine is indispensable: a blog post by Justin Sheehy -
Resources, For Real This Time (with Webmachine): a video by Sean Cribbs -


bugs may be submitted through


  • Stevan Little <>

  • Dave Rolsky <>


  • Andreas Marienborg <>

  • Andrew Nelson <>

  • Arthur Axel 'fREW' Schmidt <>

  • Carlos Fernando Avila Gratz <>

  • Fayland Lam <>

  • George Hartzell <>

  • Gregory Oschwald <>

  • Jesse Luehrs <>

  • John SJ Anderson <>

  • Mike Raynham <>

  • Nathan Cutler <>

  • Olaf Alders <>

  • Stevan Little <>

  • Thomas Sibley <>


This software is copyright (c) 2016 by Infinity Interactive, Inc.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.