#!/usr/bin/perl

use 5.010;
use strict;
use warnings;
use IO::Socket::INET6;

my $pid = fork;

die "error: cannot fork!\n" unless defined $pid; # edit

my $server = IO::Socket::INET6->new(
    LocalAddr => $pid ? '127.0.0.1' : '::1',
    LocalPort => 20_000,
    Listen    => 5,
    Proto     => 'tcp',
    ReuseAddr => 1,
) or die "error creating socket: $@\n";

while (my $client = $server->accept) {
    chomp(my $request = <$client>);

    if ($request =~ /^quit|exit|bye/) {
        print $client "exiting\n";
        close $client;
        exit; # es wird nur der beendet, mit dem verbunden wurde. nicht beide
    }

    print $client (scalar reverse $request), "\n";
    close $client;
}