What does <<-CONSTANT do?

Question

return <<-HTML
  <li>
    <a href = "some-link">Link-Title</a>
  </li>
HTML

What are <<-HTML on the first line and HTML on the last line for?

Answer 1

It's a heredoc.

http://en.wikipedia.org/wiki/Here_document#Ruby

Answer 2

That's a here document. Basically, it's a multi-line string literal.

On lines after the line with the <<-HTML, those are literal strings concatenated by newlines-- until the end marker is reached, which in this case is HTML.

Answer 3

To explicitly answer the question, this snippet returns the string:

<li>

<a href = "some-link">Link-Title</a>

</li>