Hook CONSTANT-like in Ruby

const_hook.rb

module M
  REAL_CONST = 'foo'

  def self.const_missing(name)
    if name == :MISSING_DUMMY
      'qux'
    else
      super
    end
  end

  def self.dummy_non_const
    'bar'
  end

  def self.DUMMY_CONST
    'baz'
  end
end

puts M::REAL_CONST
puts M::MISSING_DUMMY
puts M::dummy_non_const
puts M::DUMMY_CONST

foo
qux
bar
const_hook.rb:8:in `const_missing': uninitialized constant M::DUMMY_CONST (NameError)
	from const_hook.rb:24:in `<main>'