two newbie questions

[ry]

1. I find myself calling %action and %eof(action) a lot. for example:
    string = ( any - pair_sep )* >string_mark %string_store
%eof(string_store);
 if I wanted to parse the string "hello".

2. I want to change a machine slightly based on input to a program. I
just would like to change one
  sep = '&';
to
  sep = ',';

Thanks
ry