use strict;
use IO::Socket;
use IO::Select;

#set up some handles


my $h1 = IO::Socket::INET->( LocalPort => $port_1, 
              Proto => 'udp'
) or die "Couldn't start upd listen on $port_1: $@\n";
my $h2  = IO::Socket::INET->( LocalPort => $port_2, 
              Proto => 'udp'
) or die "Couldn't start upd listen on $port_2: $@\n";


my $readable_h = new IO::Select();
$readable_h->add($h1);
$readable_h->add($h2);


while (1) {
    my @readable = $readable_h->can_read($timeout);
    foreach my $sock (@readable) {
        $buf = <$sock>
    #
    ## do something with buf
        #
    }
}
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Coded quickly mising detail but should give you the right idea.

mitd-Made in the Dark
'My favourite colour appears to be grey.'