Thanks for looking at this so carefully. I should have mentioned in my original post that I did indeed try the suggestion in the docs of renaming the script and made matching changes to the .htaccess file.

I'm not sure how to tell whether the server is handling a script as cgi or fast_cgi. Is there a way to determine this? (I thought adding an AddHandler in the .htaccess file forced this, but that's merely an assumption I made looking at the material at the links above.)