nested content in rails view helpers

nested_content_snippet.rb

  # because i can never remember exactly how and when to use concat
  # when building content in helpers
  def nested_content
    content_tag 'div' do
      concat(content_tag 'span', 'span block')
      concat(tag 'br')
      concat(link_to 'root link', root_path)
      concat(tag 'br')
      concat(link_to('#') do
               concat(content_tag 'h2', 'Head \'em off')
               concat(tag 'br')
               content_tag 'div', (content_tag 'span',(concat 'dudue'))
             end)
    end
  end