The script itself is pretty straight-forward: it creates a server object using IO::Socket::INET and attaches that socket to an AnyEvent IO eventloop. Furthermore, upon every connection, it will call the subroutine fork_call (which is in the AnyEvent::Util module) to open up a client socket.

 
#!/usr/bin/env perl 
use strict;
use warnings;
use utf8;

use IO::Socket::INET;
use AnyEvent;
use AnyEvent::Util;
$AnyEvent::Util::MAX_FORKS = 15;

my $handled = 0;
$|++;

my $server = IO::Socket::INET->new(
    'Proto'     => 'tcp',
    'LocalAddr' => 'localhost',
    'LocalPort' => 1234,
    'Listen'    => SOMAXCONN,
    'Reuse'     => 1,
) or die "can't setup server: $!\n";
print "Listening on localhost:1234\n";

my $cv = AnyEvent->condvar;
my $w; $w = AnyEvent->io(
        fh   => \*{ $server }, 
        poll => 'r', 
        cb   => sub { 
                   $handled++;
                   $cv->begin; 
                   fork_call &handle_connections, 
                             $server->accept, 
                             sub { 
                               my ($client) = @_ ;
                               print " - Client $client closed\n"
                             } 
                    }
);
$cv->recv;

#
# Subroutines
# 
sub handle_connections {
    my ($client) =  @_;

    my $host = $client->peerhost;
    print "[Accepted connection from $host]\n";

    print $client "Hi, you're client #$handled\n";
    chomp ( my $input = <$client> );
    my $output = reverse $input;
    print $client $output, "\n";
    print $client "Bye, bye.\n";

    $cv->end;
    return $host;
}