I thought that will work, but not worked

use HTTP::Server::Simple::PSGI;
my $app = sub {
    my $env = shift;
    return sub {
        my $responder = shift;
        my $writer = $responder->([ 200, [ 'Content-Type' => 'text/pla
+in' ]]);
        my $n = 0;
        $writer->write($n);
        $n++;
        sleep 1;
        $writer->write($n);
        $n++;
        sleep 1;
        $writer->write($n);
        $n++;
        sleep 1;
        $writer->write($n);
        $n++;

    };
};
my $server = HTTP::Server::Simple::PSGI->new('8080');
$server->app($app);
$server->host('127.0.0.1');
$server->run();
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