As I have just figured out after some of the upgrades the external link in the title hack was, indeed, broken. In fact, I am somewhat puzzled, as it worked on some of my installations and didn’t work on others.
It turns out that the method of obtaining the permalink for the post is returning the canonical URI no matter what permalink system has been set up (I use custom on this blog). For example, even if you have something SEO-friendly, the code
$perm = $post_id->guid;
$perm = get_permalink($post_id);
That’s it. Should work.
P.S. Updated the downloadable txt file. Click here to view.