One more thing: talexb suggested to get your JSON from somewhere out there as far as i understood.

This idea seems to be fairly elegant. As you don't need to throw away your Apache/mod_perl stuff etc.

What about this little sketch?

# app.psgi
use strict;
use warnings;
use Plack::Request;
use Plack::App::URLMap;
use JSON::Tiny qw(encode_json);

my $slash = sub {
    my $env = shift;
    my $json = encode_json {nose => 'cuke'};
    my $status  = 200;
    my $request = Plack::Request->new($env);
    my $headers = [
        'Content-Type'   => 'application/json',
        'Content-Length' => length $json,
    ];
    my $body = [ $json ];
    [ $status, $headers, $body ];
};

my $urlmap = Plack::App::URLMap->new;

$urlmap->mount( "/" => $slash );

my $app = $urlmap->to_app;

__END__
[download]

Then: starman --listen /tmp/starman.sock.

And then try: echo -e "GET / HTTP/1.0\r\n" | nc -U /tmp/starman.sock.

This should yield:

HTTP/1.0 200 OK
Content-Type: application/json
Content-Length: 15
Date: Tue, 26 Oct 2021 14:25:29 GMT
Connection: close

{"nose":"cuke"}
[download]

See also Plack::Request and Plack::App::URLMap.

The other links you have already.

Probably Try::Tiny might be helpful for handling malformed JSON.

Regards, Karl