set_parse_mode() and triggering W08

Hi all,
Congrats on the new version of the validator. IMO the new look is a
big improvement on the old one. I have a question about the check
script, and I hope it isn't out of place here.

I'm trying to understand the conditions under which the validator will
generate certain warnings. The function set_parse_mode() in check can
trigger warnings W06 and W08 which are similar. I can trigger W06 by
validating a document that meets these conditions:
- Mime type = text/html
- Doctype either absent or FPI not in the validator's catalog
- No XML declaration.

Looking at the check script, I *thought* this would trigger W08 via
the test on line 1979. I can't figure out (a) why it didn't and (b)
how to do so. The fact that I don't know Perl probably has something
to do this... I'd very much appreciate it if someone could give me a
hint as to how to trigger W08.

Thanks

-- 
Philip
http://NikitaTheSpider.com/
Whole-site HTML validation, link checking and more