Perl RawIP CWR Flag

I'm using Net::RawIP to send packets with specific TCP flags. Is there a way to set the CWR flag? TCP protokey "res2" sets the ECE flag, but "res1" seems to set the NS flag:

$n = Net::RawIP->new({
ip  => {
        saddr => 'my.target.lan',
        daddr => 'my.target.lan',
       },
tcp => {
        source => 123,
        dest   => 123,
        res1   => 1,
        res2   => 1,
        fin    => 1,
        syn    => 1
       }
});

Here's a Wireshark capture of the packet's flags: