Simple type safe enum in Ruby

module Kernel
  def enum(*syms)
    new_class = Class.new do
      def initialize(name)
        @name = name
      end
      def to_s
        "#{self.class.name}::#{@name}"
      end
    end
    syms.each { |type| new_class.const_set(type, new_class.new(type)) }
    new_class
  end

  def enum2(*syms)
    syms.each do |sym|
      e = Object.new
      e.instance_eval("
        def to_s
          \"#{self}::#{sym.to_s}\"
        end
      ")
      const_set(sym.to_s, e)
    end
  end
end

Above is two types of type safe(I believe :-) Enum.

First type is constant defining style. For example

InstrumentType = enum :GUITAR, :BANJO, :DOBRO

Second type is including style. For example,

module InstrumentType
  enum2 :GUITAR, :BANJO, :DOBRO
end

What do you think about above code? Which one is better?