sub foo : lvalue { $dat{ +shift }->{ 'foo' } }

##</code><code>##

  dat_attr foo;

##</code><code>##

package Class::Attr::Lvalue;
use Filter::Simple;
FILTER
{
   s/(\w+)_attr (\w+)(\s*);/sub $2$3: lvalue { \$$1\{ +shift }->{ '$2' $3 } }/g;
#   print;
}
1;