Thanks for the notes.
In reply to your comment however:
I believe PHP has spread more because ready-to-install scripts like vB, phpBB, phpNuke, Typo3 and others are available that allow "non-techies" to run dynamic content on their sites.
Before the advent of virtual hosting PHP, the most widespread messageboard software was UBB - written in Perl, with very ugly internals and hard to customize. But it was successful, because at the time it was released, no other messageboard software offered a "control panel" for easy configuration - you had to edit text files and/or the scripts themselves.
PHP won, because it was easy to offer for hosts and easy for technically unsavvy site owners to run scripts for it. You already mentioned Template Toolkit II - having Apache::Registry applications use it (or maybe Mason?) would make them about as easily customizable as comparable PHP applications.
That alone should be a great boost; and of course, for the savvy folks it would be a conditioning drug, who will soon want harder stuff like real mod_perl handlers. :)
Makeshifts last the longest.