I forgot to include some example code in my original submission:
<?
$t = new template($templateDir);
$t -> set_cache(array("name" => "cachetest", "timeout" => 10));
$t -> set_file("main", "index.ihtml");
$t -> pparse("output", "main");

echo "this is not a cache.  This text will not appear on a cached page.";
?>

Thanks, Tom