Include Case-Insensitive

Sort of. You can't expect to change ruby's constant system to be
insensitive, but if you're OK with passing in strings, this might
work:

class Module
  def include_insensitive(*args)
    args.each do |m|
      include(const_get(Module.constants.grep(/^#{m}$/i).first))
    end
    self
  end
end

module M
  def im_in_m
    :hi
  end
end

class C
  include_insensitive "m"
end

C.new.im_in_m #=> :hi