my $hSocket = IO::Socket::INET->new(
    LocalPort=>$intListenPort, 
    Proto=>$strProtocol
) or die "Can't create UDP socket: $@";
ioctl($hSocket, 0x8004667e, pack("I", 1));

my( $gotone, $datagram, $flags) = 0;
my $endtime = time() + $timeout;
while( time() < $endtime ) {
    sleep 1 and next unless $hSocket->recv($datagram,42,$flags );
    ## Got a datagram.
    ...
    $gotone = 1;
    last;
}
if( $gotone ) {
    ## We processed a datagram within the timelimit
}
else {
    ## we didn't
}