#!/usr/bin/perl
use strict;
use warnings;
use IO::Socket;
use IO::Select;
use Tie::RefHash;

my ( %connections );
tie %connections, qw( Tie::RefHash ); # so we can use refs as hash keys

my $server = IO::Socket::INET->new(
				   Listen    => SOMAXCONN,
				   LocalPort => $opts{port},
				   Reuse     => 1,
				   Proto     => 'tcp',
				  )
  or die "can't open connection: $!";
$server->blocking( 0 );

my $select = IO::Select->new( $server );

while('eternity'){
    foreach my $con ( $select->can_read(1) ) {
    #another way is to let it block, instead of passing can_read a timeout, but I usually need to check state, maybe send new output, so I need to loop often

	if ( $con == $server ) {
	    # looks like we have a new user connection
	    $client->blocking( 0 );
	    $select->add( $client );
            #whatever you want to store about the client can go in the value, I like using a hashref so I'm not limited
	    $connections{$client}{ip} = $client->peerhost;
	}
	elsif ( exists $connections{$con} ) {
	    # I guess it's a connected user sending us data
	    ...
	}
	else {
	    #whoops, unknown filehandlw
	}
}