use Device::SerialPort;

my $port = new Device::SerialPort("/dev/ttyACM0"); 
$port->user_msg('ON'); 
$port->baudrate(9600); 
$port->parity("none"); 
$port->databits(8); 
$port->stopbits(1); 
$port->handshake("xoff"); 
$port->write_settings;

$port->lookclear; 

my $is_writting = 0;
my $i = 0;
while (1) {
    my ($count, $saw) = $port->read(1);
    $i++;
    if ($count < 1) {
        if ($is_writting) {
            print "\n";
            $is_writting = 0;
            $i = 0;
        }
        next;
    }
    print $saw;
    $is_writting = 1;
}