In other words, you're saying that they *can* share the cookie.

Yes, www.perlmonks.org and perlmonks.org can share a cookie. And they do, so long as you log into perlmonks.org rather than www.perlmonks.org. Similarly with the .net and .com pairs. What can't be done is sharing cookies across domains. There are a number of reasons the spec doesn't allow for that, security not least among them.

-sauoq
"My two cents aren't worth a dime.";