I use both and have never had a problem. I log into perlmonks.org and can temporarily "log out" by adding the www. to the browser URI box and hitting enter. It's a matter of which URI the cookie is assigned to: www.perlmonks.org can have a different cookie than perlmonks.org.

Why do i do this? Just to quickly verify what the diff between my user CSS and the default CSS is. Please don't attempt this trick to manage mulitple accounts, as the gods will most likely find out and possibly take away your voting priviledge.

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)