my $nonblocking = 1;
ioctl($sock, 0x8004667e, $nonblocking) or die "ioctl socket: $!\n";
my $sockread = sysread($sock, $buffer, $chunk); #should be non-blocking
$nonblocking = 0;
ioctl($sock, 0x8004667e, $nonblocking) or die "ioctl socket: $!\n";
$sockread = sysread($sock, $buffer, $chunk); #should block