gistfile1.txt

v6;

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

# default result
class BuuAbc0 {
    method TOP($/) { make $/; }
    method abc($/) { make $/; }
    method bc($/) { make $/; }
    method c($/) { make ~$/;  }
};

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 !
};

class BuuAbc3 {
    method TOP($/) { make ~$<abc>>>.ast; }
    method abc($/) { make ~$<bc>>>.ast; }
    #method bc($/) { make ~@$<c>>>.ast; }
    method bc($/) { make ~$<c>>>.ast; }
    method c($/) { make 3;  }
};

class BuuAbc4 {
    method TOP($/) { make $<abc>>>.ast; }
    #method abc($/) { make $<bc>>>.ast; }
    method abc($/) { make ~@$<bc>; }
    method bc($/) { make ~@$<c>>>.ast; }
    method c($/) { make 3;  }
};

class BuuAbc5 {
    method TOP($/) { make $/; }
    method abc($/) { make $/; }
    method bc($/) { make $/; }
    method c($/) { make 3;  }
};

class BuuAbc6 {
    method TOP($/) { make $/<abc>>>.ast; }
    method abc($/) { make $/; }
    method bc($/) { make 'cb'; }
};

my $r = BUU.parse( "abcabccabbccaababc", :actions( BuuAbc6 ) );

say $r.ast;