I'm preparing a talk about Perl6 for the Italian Perl Workshop, and I
would like to have a slide comparing a BNF (yacc/bison) grammar to a
Perl6 one, to show how powerful in parsing/lexing Perl6 regexen are.

so I ask your assistance in helping me putting up a simple, yet
impressive enough, sample.

I've taken this bison example (an RPN calculator, stripped down version
from http://www.gnu.org/software/bison/manual/html_node/Rpcalc-Rules.html):

  input:    /* empty */
          | input line
  ;

  line:     '\n'
          | exp '\n'
  ;

  exp:      NUM
          | exp exp '+'
          | exp exp '-'
          | exp exp '*'
          | exp exp '/'
  ;
  %%

and this is my attempt at a "port" to Perl6:

  grammar RPN {
      rule input { <line>* }
      rule line { <exp>? \n }
      rule exp {
          [ NUM
          | <exp> <exp> <'+'>
          | <exp> <exp> <'-'>
          | <exp> <exp> <'*'>
          | <exp> <exp> <'/'>
          ]
      }

      rule NUM { \d+ } # could be more complex, I know :-)
  }

  if $data ~~ RPN.input { say "valid RPN data" }

am I missing something obvious here? will the above code work in Perl6?
do you have perhaps a better example, or just an idea about what to show?

cheers,
Aldo