[RVuRnvbM2e]

Do you mean the optional type enforcement? Admittedly it's not built-in to ruby, but it's easy to replicate.. and a lot less verbose:

  # Implementation:
  
  module TypedAttrs
      def attr_accessor_type name, type
          define_method name do
              instance_variable_get "@#{name}"
          end
          define_method "#{name}=" do |value|
              raise ArgumentError unless value.is_a? type
              instance_variable_set "@#{name}", value
          end
      end
  end
  
  # Example:
  
  class Foo
      extend TypedAttrs
      attr_accessor_type :bar, Integer
  end
  
  a = Foo.new
  
  a.bar = 5
  p a.bar
  a.bar = "hi" # ArgumentError

[csirac2]

Sure. And just for attributes, there's also delegation, read-only attributes, builders, lazy init, roles, modifiers which are enforced at construction time (if `required` is true).

Moose isn't hard to implement, it's actually had quite a few alternate implementations even in Perl. Python has enthought's traits package, and I've just been pointed to https://github.com/frasertweedale/elk as well.

BTW it sucks to nit-pick, but the Moose version isn't any more verbose than yours:

    package Foo;
    use Moose;
    has 'bar' => ( isa => 'Integer' );