Ruby instance_eval scope issue I don't understand.

instance_eval_module_scope.rb

module Bar
  module Baz
  end

  def hi_there
    puts 'Hi!!'
  end
end

class Foo
  include Bar

  def initialize(&block)
    puts "Baz is available in this context: #{Baz.inspect}"
    instance_eval(&block)
  end
end

Foo.new do
  hi_there
  puts "Global reference works ok: #{Bar::Baz.inspect}"
  puts "Why isn't Baz found? #{Baz.inspect}" # NameError: uninitialized constant Baz 
end

instance_eval only changes self. All non-instance variables (incl classes/modules) are not affected and retain the binding of when the block was defined.