Yes, I tried your code:
PHP Code:
$template_hook['headinclude_javascript'] .= 'test';
and then in the html I got this:
Code:
var RELPATH = "";
var PATHS = {forum : ""}
// -->
</script>
<script type="text/javascript" src="http://10.0.0.4/forum4/clientscript/vbulletin-core.js?v=415"></script>
test
<link rel="alternate" type="application/rss+xml" title="Forums 4.1.5 RSS Feed" href="http://10.0.0.4/forum4/external.php?type=RSS2" />
But it did seem like the first time I did it it didn't work, so maybe there's some caching going on or something.