- experimental
- allow header and footer in eRuby script
ex.
  ====================
  ## without header and footer
  $ cat ex1.eruby
  <% def list_items(list) %>
  <%   for item in list %>
  <li><%= item %></li>
  <%   end %>
  <% end %>
  $ erubis -s ex1.eruby
  _buf = []; def list_items(list)
  ;   for item in list
  ; _buf << '<li>'; _buf << ( item ).to_s; _buf << '</li>
  ';   end
  ; end
  ;
  _buf.join
  ## with header and footer
  $ cat ex2.eruby
  <!--#header:
  def list_items(list)
   #-->
  <%  for item in list %>
  <li><%= item %></li>
  <%  end %>
  <!--#footer:
  end
   #-->
  $ erubis -s -c HeaderFooterEruby ex4.eruby
  def list_items(list)
   _buf = []; _buf << '
  ';  for item in list
  ; _buf << '<li>'; _buf << ( item ).to_s; _buf << '</li>
  ';  end
  ; _buf << '
  ';
  _buf.join
  end
  ====================
this is language-independent.