actually, it's 6: with and without www., so you can be logged in with 6 different user names at the same time (or test how it looks like from a non-logged-in user while being logged in in another tab).

https://www.perlmonks.com/	https://perlmonks.com/
https://www.perlmonks.net/	https://perlmonks.net/
https://www.perlmonks.org/	https://perlmonks.org/