RosettaCodeData/Task/Digital-root/Perl-6/digital-root-2.pl6

sub digroot ($r, :$base = 10) {
    my &sum = { [+](.comb.map({:36($_)})).base($base) }

    return .[*-1], .elems-1
        given $r.base($base), &sum ...  { .chars == 1 }
}