>Number 4 and 5 fail because the regex is looking for To: 
>"something between quotes".... There are no quotes at all, 
>so it fails quickly, and failure equals not-spam, so they're 
>both not spam.

I get it. No.5 is not spam for this regex filter. NO.4 and No.5 fails because simply double quotes doesn't exist! I was totally confused with your comment below.

# The email address should be "Furry Marmot" <marmot@furrytorium.com>, or just
# marmot@furrytorium.com. Anything else is spam.

I was thinking that there must be some magic to judge "just <test@furrytorium.com>" as a Spam. But test script says it is not a Spam...??? Now it's clear.

Anyway I should look perlre also. Thanks for kind explanation to a bad student. regards.