module A; end
module B;
  module C; end
  module D; end
end

QQQ = B::D

class X
  include A
  include B, B::C, NOTEXIST
end

module Y
  include B::C, B if X == 2
  include A
  include QQQ

  class << self; include A; end
end

module Z
  include A, B
end

module ABC
  module FOO; end
  module DEF
    module FOO
      include ABC::FOO
    end

    module BAR
      include ABC::BAR
    end
  end
end