Did you know that Perl 5 subroutine attributes can apply to forward declarations even if there's no full declaration later? I thought this was true, but I had to make sure.
You can get rid of a lot of unnecessary code with these tricks. (I like Attribute::Handlers a lot.)
use Test::More tests => 1;
use P5NCI::Attribute library => 'nci_test', path => 'src';
:NCI( double_int => ii );
is( double_int( 10 ), 20, 'NCI attribute should install named thunk' );
I don't know if general purpose NCI can get much shorter than this, but I like it.