> $VERBOSE = true
=> true
> s1 = String.new
=> ""
> s2 = String.new
=> ""
> class << s1
>   S1 = 1
> end
=> 1
> S1
NameError: uninitialized constant S1
	from (irb):9
> String::S1
NameError: uninitialized constant String::S1
	from (irb):10
> s1::S1
TypeError: (null) is not a class/module
	from (irb):11
> s2::S1
TypeError: (null) is not a class/module
	from (irb):12
> class << s1; p S1; end
1
=> nil
> s3 = s1.dup
=> ""
> class << s3; p S1; end
NameError: uninitialized constant String::S1
	from (irb):15
> s4 = s1.clone
=> ""
> class << s4; p S1; end
1
=> nil
> class << s1; self.constants; end
=> ["S1"]
> class << s2; self.constants; end
=> []
> class << s3; self.constants; end
=> []
> class << s4; self.constants; end
=> ["S1"]