Insertion location

A minor adjustment will fix this: in perpagehead.php, line 110, replace add_action('wp_head', 'perpageath_display'); with add_action('wp_head', 'perpageath_display', 1000000); or a larger number. This will put my plugin way down the queue on the wp_head hook.

However, sometimes a theme developer manually adds stuff to the head segment after calling the wp_head hook. If that is the case, this won’t work, and you should contact your theme developer.