#!/usr/bin/perl -w
use strict;
use warnings;
use IO::Socket::INET;

my $socket = IO::Socket::INET->new (
    PeerHost => "X.X.X.X",
    PeerPort => "9000",
    LocalHost => "Y.Y.Y.Y",
    LocalPort => "9001",
    Listen    => SOMAXCONN,
    Reuse     => 1
)
or die "Can't connect to socket: $!\n";

while (my $client = $socket->accept) {
    my $pid = fork();
if ($client->peerhost() = X.X.X.X)
    if ($pid == 0) {
        handle_client($client)
    }
...
}