Ruby TMail detect HTML in plain text or escaped HTML

gistfile1.rb

class TMail::Mail
  def bad_html?
    if multipart?
      return true if parts.detect{|p| p.content_type.include?('text/plain') && p.to_s =~ /<(html|head)/im }
      return true if parts.detect{|p| p.to_s =~ /&lt;\/(p|a|span|div|style|head|html)&gt;/im }
    else
      return true if body =~ /&lt;\/(p|a|span|div|style|head|html)&gt;/im
      return true if content_type.include?('text/plain') && body =~ /<(html|head)/im
    end
    false
  end
end