[ammon]

Hmm. Just checked again. Two of the expressions match neither word, one matches both, and one matches only one.

EDIT: I see. The confusion is over partial match vs whole match. I thought whole matches were standard when talking about regular expression in the abstract, but looks like I was wrong. Just changed the problem to include the anchors. Thanks for pointing this out.

[ibdknox]

That's not the standard meaning in my experience. Regex's are often used for extracting information from larger strings, forcing a full match by default would be pretty counter to their purpose.