...does not work. I do understand why this is as $v can only access items on the page. However, APEX is clearly able to obtain such global values since, for example, they are available in PL/SQL blocks. Also, I know it's on the session object because I can see it when viewing the session.
$v( 'DEFAULT_AJAX_SEPERATOR' );
var default_ajax_separator = &DEFAULT_AJAX_SEPERATOR.