1.3.2 クラス再訪
irb(main):078:0> "Hello".class => String irb(main):079:0> String.class => Class irb(main):080:0> String.superclass => Object irb(main):081:0> Object.superclass => BasicObject irb(main):082:0> BasicObject.superclass => nil irb(main):083:0> Class.superclass => Module irb(main):084:0> Module.superclass => Object irb(main):086:0> Class.class => Class