PSGI library stack for Perl6
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Crust - Perl6 Superglue for Web frameworks and Web Servers


Crust is a set of tools for using the PSGI stack. It contains middleware components(TBI), and utilities for Web application frameworks. Crust is like Perl5's Plack, Ruby's Rack, Python's Paste for WSGI.

See PSGI for the PSGI specification.



Crust::Handler and its subclasses contains adapters for web servers. We have adapters for the built-in standalone web server HTTP::Easy::PSGI, and HTTP::Server::Tiny included in the core Crust distribution.

See Crust::Handler when writing your own adapters.


P6SGI middleware is a P6SGI application that wraps an existing P6SGI application and plays both side of application and servers. From the servers the wrapped code reference still looks like and behaves exactly the same as P6SGI applications.

Crust::Request, Crust::Response

Crust::Request gives you a nice wrapper API around PSGI $env hash to get headers, cookies and query parameters much like Apache::Request in mod_perl.

Crust::Response does the same to construct the response array reference.

.p6sgi files

A PSGI application is a code reference but it's not easy to pass code reference via the command line or configuration files, so Crust uses a convention that you need a file named "app.p6sgi" or similar, which would be loaded (via perl6's core function "EVALFILE") to return the PSGI application code reference.

# Hello.p6sgi
my $app = sub ($env) {
    # ...
    return $status, $headers, $body;

If you use a web framework, chances are that they provide a helper utility to automatically generate these ".p6sgi" files for you, such as:

# MyApp.p6sgi
use MyApp;
my $app = sub { MyApp->run_psgi(@_) };

It's important that the return value of ".p6sgi" file is the code reference. See "eg/" directory for more examples of ".p6sgi" files.

An Alternative to .p6sgi files

As an alternative to using EVAL, you can take advantage of Perl's Callable type which will return a code reference as well, making Crust happy.

Here is an example of an implmentation using a Callable class in place of any .p6sgi files and having to call a "crustup" script. You can call this directly from the command line, just like you would "crustup".

use v6;

use Crust::Runner;

class MyApp does Callable
    has $.status  is rw;
    has @.headers is rw;
    has @.body    is rw;

    method CALL-ME(%env) {;

    method call(%env) {

        $.status  = 200;
        @.headers = [ 'Content-Type' => 'text/html' ];
        @.body    = [ '<html><head><title>Hi</title></head>',
                      '<body>I just want you to see me</body>',

        return $.status, @.headers, @.body;

my $runner =;


  • Tokuhiro Matsuno

  • mattn

  • Shoichi Kaji

  • Daisuke Maki

  • moznion

  • Kentaro Kuribayashi

  • Tim Smith

  • fayland


Copyright 2015 Tokuhiro Matsuno

This library is free software; you can redistribute it and/or modify it under the Artistic License 2.0.