RCS 5.9.4: problem "badly terminated keyword value" for "ci -k"

Hi!

I have an unsolvable problem with RCS 5.9.4, that probably could need:

* either an option to ignore this error
* an improved parser for keywords.

In any case a better diagnostic message (which keyword, BTW?) would be =
helpful.
So here is what I have: I had copied a file from another computer that is =
checked out by RCS. The local computer didn't have the latest version, so =
I wanted to check it in:

ci -d -k -u -M ./pwg.pl=20
./RCS/pwg.pl,v  <--  ./pwg.pl
ci: ./pwg.pl: badly terminated keyword value

So you have no idea what "keyword" actually causes the problem. However =
ident can provide some clues:

pwg.pl:
     $Id: pwg.pl,v 5.2 2019/01/31 11:47:13 windl Exp $
     $selector: unknown domain specifier $
     $selector: unknown random selector $
     $op: ", $

Here also ident could use an option that displays line numbers for the =
"keywords" also ;-)

The source lines causing the problems actually are:

warn "$selector: unknown domain specifier $1\n";
warn "$selector: unknown random selector $selector\n";
print "Entropy before $op: ", $e->as_string(), "\n"

Is there any chance to check-in the source unmodified? (I could replace =
all "$foo" with "${foo}")

Regards,
Ulrich
P.S. I'm not subscribed to the mailing list, so please keep me on CC: