Defining $templatesused before requiring global.php will cache those templates. For example:
PHP Code:
$templatesused = "mytemplate,anothertemplate";
require("./global.php");
...will cache those two templates. If you don't do that and then later in the file try to eval either template, it will create an extra query.
IMO I think it's a pretty dumb system; a better way (again, IMO) would be to associate each template with one or more PHP files, and then have the template engine automatically cache all necessary templates for that file.