Which PHP variables are available in pattern?

Switching to 7.x branch, as 6.x is no longer supported, but the question is still relevant.

Have you seen other modules list out the variables available in a similar "evaluate php" type field? In the 7.x branch at least, there is a note saying that the $account object is available. Is that sufficient?

I actually think this "evaluate php in pattern" option should be removed from the module (for security reasons) in favour of developers implementing hook_auto_username_name() in their modules code. But we'll wait for feedback from other users of the module first, before removing it.