package Obj; 
use Moose; 
 
has "num" => ( 
	is => "ro", 
	isa => "Int", 
	default => 10 
); 
 
package Main; 
 
my $o1 = Obj->new(); 
 
$o1->{num} = 20; 
 
print $o1->num; # return 20, but "num" atrtribute is read-only ??, ..