Is there a way to include HTML from a file in the "overall_header.tpl" file?

I'm posting this on the phpbb forums as well, but they can be pretty unhelpful over there.

A quick look at the code shows that it's actually pre-pending an "echo" to every line in the template when it is parsed, so a simple <?php include('included-file.html'); ?> will not work as it would end up just being echo'd into the final html and never executed. Easiest solution would be to just cut and paste your html into the template file, that's what it's there for.