    # File lib/core-uncommon/facets/module/let.rb, line 13
      def let(var,&block)
        name = "@#{var}"
        self.class_eval do
          define_method(var) do
            if instance_variable_defined?(name)
              instance_variable_get(name)
            else
              val = self.instance_eval(&block)
              instance_variable_set(name,val)
            end
          end
        end
      end