Here's a few examples:
"this is #$$"
var = $!
Things are different for:
"this is #$1"
var = $1
Have you tried it in the latest Emacs? For me, only one example
"this is #$$"
is not highlighted (I'll fix that).
There's another thing to consider - do built-in global vars should be
font-locked like built-ins or like the other (user-defined) global
variables? Personally I'd font-lock them as built-in to underline their
significance.
Hmmm, maybe. But we also highlight nil, self, true, false, __LINE__,
__ENCODING__ and __FILE__ with font-lock-variable-name-face. Should we
change these, too?