--- instance_variable_set(var, val)

    ruby 1.8 feature

    ֥ȤΥ󥹥ѿ var ͤ val ꤷ
     val ֤ޤ󥹥ѿƤʤ 
    󥹥ѿޤ󥹥ѿ̾ var ʸ
     Symbol ǻꤷޤ

        obj = Object.new
        p obj.instance_variable_set("@foo", 1)  # => 1
        p obj.instance_variable_set(:@foo, 2)   # => 2
        p obj.instance_variable_get(:@foo)      # => 2

