use Proc::Fork;
use IO::Pipe;

my ($pipe) = new IO::Pipe;

child {
    $pipe->reader();
    while (1) {
        while ($num = <$pipe>) {
        }
        print "Child: $num\n" if $old_num != $num;
        $old_num = $num;
        last if $num == 644;
    }
    exit;
};
$pipe->writer();
while (1) {
    $in = <>;
    chomp $in;
    print $pipe $in;
    last if $in == 644;
}