my $dnspacket = new Net::DNS::Packet( 'www.google.com, 'IN', 'ANY' );
$dnspacket->header->qr(0); #Query Responce Flag
$dnspacket->header->aa(0); #Authoritative Flag
$dnspacket->header->tc(0); #Truncated Flag
$dnspacket->header->ra(0); #Recursion Desired
$dnspacket->header->rd(1); #Recursion Available
$udp_max = $dnspacket->header->size(1024);