Calling html_safe on a heredoc stalls development server

This helper works (in application_helper.rb):

  def facebook_button(options={})
    markup = ''
    markup += "<a class=\"fb_button fb_button_medium\" href=\"#{options[:link]}\">"
    markup += "<span class=\"fb_button_text\">#{options[:text]}</span>"
    markup += "</a>"

    markup.html_safe
  end

But this makes the development server stall in a way that only a kill -9 closes it:

  def facebook_button(options={})
    <<-markup
    <a class="fb_button fb_button_medium" href="#{options[:link]}">
      <span class="fb_button_text">#{options[:text]}</span>
    </a>
    markup 

    markup.html_safe
  end

I actually don't assign the heredoc :D but it shouldn't get stuck... right?

I'm on Arch Linux x86_64, using Rails 3.0.4 on REE 2011.03. I tried both WEBrick and Thin (1.2.8).

Thanks,

Bruno A.