you don't need break indents.

heredocument.rb

#! /usr/bin/env ruby

class Poem
  def initialize
    @text = <<-END.gsub(/^\s+/,'')
      この支配からの卒業
      (尾崎豊)
    END
  end
  def shout
    puts @text
  end
end

Poem.new.shout