This is almost exactly what I'm doing. Except that to keep "consistent" I set the values I want to be "undefined" to '?'. As I wrote, I feel uneasy with this setup. Building the whole of @binds at execution time sounds like being more error prone, since if I change the clause, I will most probably also have to change the code that builds it, and if I forget to, then... I will screw it all up. I'd like to minimize the chances to do so instead!