This is an idiom I use regularly (in Perl, Ruby, Io & Javascript) and come across it often in the Perl world where Moose roles are used. The only downside of t

This is an idiom I use regularly (in Perl, Ruby, Io & Javascript) and come across it often in the Perl world where Moose roles are used. The only downside of this idiom is the extra runtime cost which maybe an issue for Rails?