with an underscore, since you will want this to be private the vast
majority of the time.
+Note that the C<builder> method name is created by simply taking
+"_build_" and appending the attribute name. This means that attributes
+with a leading underscore like C<_animal> end up with a builder named
+C<_build__animal>.
+
=head1 CONCLUSION
The C<builder> option is a more OO-friendly version of the C<default>