Simple echo server in response to https://blog.afoolishmanifesto.com/posts/concurrency-and-async-in-perl/

echo.pl

#!/usr/bin/env perl
use Mojo::Base -strict;
use Mojo::IOLoop;

Mojo::IOLoop->server({ port => 9934 }, sub {
  my ($ioloop, $stream) = @_;
  my ($disconnect, $id);

  $disconnect = sub {
    warn "client disconnected\n";
    Mojo::IOLoop->remove($id); # clean up recurring timer
  };

  $stream->on(close => $disconnect);
  $stream->on(error => $disconnect);
  $stream->on(read => sub { $_[0]->write($_[1]); });

  $id = Mojo::IOLoop->recurring(5 => sub { $stream->write("ping!\n"); });
});

Mojo::IOLoop->start;