PSGI: Failed to run Perl Application: 
Undefined subroutine &main::1 called.

##</code><code>##

#!/usr/bin/perl

use strict;
use Mojolicious::Lite;

get '/' => {text => 'Hello World'};

app->start;

##</code><code>##

{
   "type": "perl",
   "processes": 5,
   "script": "/etc/unit/app.psgi",
   "environment": {
      "MOJO_MODE": "production"
   }
}

##</code><code>##

#!/usr/bin/perl
use strict;
use warnings;
use Plack::Builder;

my $app = sub {
    my $env = shift;
    [200, [], ["Hello world from PSGI!\n"]];
};

builder {
    enable 'ContentLength';
    $app;
};