$w1 = open(fw1,"pgm1|");
$w2 = open(fw2,"pgm2|");

$read_set = new IO::Select(); 
$read_set->add($w1);
$read_set->add($w2);

while (1) { ;
	my ($rh_set) = IO::Select->select($read_set, undef, undef, 2);
	print $rh_set; 
	foreach $rh (@$rh_set) {
              ...DoSomething...
    }
}