gistfile1.txt

v6;

grammar BUU {
    token TOP { <abc>+ };
    token abc { 'a' <bc>* };
    token bc { [ 'b' <c>* ]+ }
    token c { 'c' };
};

# default result
class BuuAbc1 {
    method TOP($/) { make $<abc>>>.ast; }
    method abc($/) { make $<bc>>>.ast; }
    method bc($/) { make $<c>>>.ast; }
    method c($/) { make ~$/;  }
};

class BuuAbc2 {
    method TOP($/) { make $<abc>>>.ast; }
    method abc($/) { make $<bc>>>.ast; }
    #method bc($/) { make $<c>>>.ast; }
    method bc($/) { make ~@$<c>; }
    #method c($/) { make ~3.ast; }  # error
    method c($/) { my $c = 3; make ~$c;  }  # this do nothing !
};

my $r = BUU.parse( "abcabccaabbc", :actions( BuuAbc2 ) );

say $r;