OK, I see.

After a bit of testing with C-u C-x =, I see that with my proposed
change the sigils in 'sub test ($)' will *not* have punctuation class
as they did before the chagne.

I see these options:

1. I can try to improve the proposed change to preserve backward
compatibility - I can try to add another rule which will strictly
match only the allowed prototype-sigils $%&*;@[\]

2. discard my proposed change as it might have undesired side effects -
at this point, I don't see anything in perl-mode which depends on
these prototype-sigils having punctioation class, however, I could be
missing something.

3. accept my proposed change as-is, but we must be sure nothing will
be broken as a result.  I'm sure syntax highlighting will not be
broken (I've tested with different themes, different perl sub
definitions).

Please let me know what you think.