code blocks (:duref:`ref &lt;literal-blocks&gt;`) are introduced by ending a
paragraph with the special marker ``::``.  The literal block must be indented
(and, like all paragraphs, separated from the surrounding ones by blank lines)::

   This is a normal text paragraph. The next paragraph is a code sample::

      It is not processed in any way, except
      that the indentation is removed.

      It can span multiple lines.

   This is a normal text paragraph again.

The handling of the ``::`` marker is 