Fastest templating mechanism

Hi all, I'm working on a template system which works a bit like a text translation block. The data looks for example like: beginblock <div class="block"> endblock </div> beginauthor <span class="author"> endauthor </div> The list is going to be very large, it will have several overlays and not all pages need all items in the list. (usually just a fraction) What will be the smartest way to implement this? I need a low-memory cost and fast solution I can do it with a php script, like: $list = array( 'beginblock' => '<div class="block">', etc. ); but this will use up too much memory. I could additionally do it with a textfile, but if I need to loop through it at every lookup it will be slow.. What are your suggestions? regards, Evert