RPN calculator in Perl 6

My list mail has been very delayed, so this may be out of sequence, but
in case no one mentioned it yet:

http://sial.org/pbot/37102

(That's ruoso++'s later 37100 paste with a couple small tweaks by me.)

I wanted to shrink that even further by replacing the given/when with a
direct call of the correct op variant, but I couldn't figure out how to
do that in current Rakudo. (And just using eval inside a multi seemed
to be broken.)


-'f