How about using something like:

Identifier: ReservedWord
            { 
              print "can't use reserved word $item[1]\n"; 
              # Do the thing that makes P::RD throw an error
            }
          | IdentifierName
[download]

There is a way in P::RD to create 'error productions' I just don't remember what you have to do to make the matching of a production be a syntax error in the input.

/\/\averick
perl -l -e "eval pack('h*','072796e6470272f2c5f2c5166756279636b672');"