Mason is a templating system that can handle web requests directly via PSGI, or act as the view layer for web frameworks such as Catalyst or Dancer. In the example below, it is used on its own to create a simple application.

A basic files needed to create an app using Mason are:

  1. app.psgi
  2. requirements.txt
  3. manifest.yml

Template files are also needed, which you can read about in the Mason documentation, or in our Hello World sample app.

In the requirements.txt file, list any module requirements, with at least:


In the app.psgi file:

use Cwd qw(realpath);
use File::Basename;
use Mason;
use Plack::Builder;
use warnings;
use strict;

# Include Mason plugins here
my @plugins = ('PSGIHandler');

# Create Mason object
my $cwd = dirname( realpath(__FILE__) );
my $interp = Mason->new(
        comp_root => "$cwd/comps",
        data_dir  => "$cwd/data",
        plugins   => \@plugins,

# PSGI app
my $app = sub {
        my $env = shift;

builder {
        # Include PSGI middleware required for Helion Stackato
        enable "Plack::Middleware::ContentLength";
        enable "Plack::Middleware::ReverseProxy";

The manifest.yml file contains deployment instructions for Helion Stackato. See complete details for this file in the Manifest.yml Options section.