In response to a question I asked earlier today, cianoz provided a very helpful answer straight from the end of the perlvar man page.

However, I do make it a point to RTFM before I ask. I had already looked over perlman:perlvar on-line here and hadn't seen the section cianoz quoted. It turns out that it's one of two sections at the end of the perlvar man page ("Technical Note on the Syntax of Variable Names" and "BUGS"), that simply aren't there in the on-line document. (And they're not just missing from here, either; the perlvar doc over at is the same as the one here at perlmonks.)

My man pages are from 5.6.0, and I don't find an identifying version number in the on-lines copies, so is this just a version difference?