> $ is designator for the current PC.  I use this often to work around the
> lack of local labels (see above) as follows:
>
>         btfsc   port,bit
>         goto    action
>         btfss   port,anotherbit
>         goto    $-3
>
> But an assembler should be able to discriminate these two uses by checking
> for hexdigits following the $ sign.

A decent scanner should have no problem whatsoever distinguishing "$" as PC
from "$" as leading character for a hex number.  It's also possible to
distinguish "*" [alternate form of PC] from "*" [as a multiply] though that
is a little bit harder, and at least one assembler I used allowed the use
of "&" and "%" for octal and binary prefixes (they could also be used as
"and" and "mod" operators, respectively) though that requires parsing rather
than mere scanning.