At a minimum, you want to change your greps from doing pattern matching to doing string equality. If there's much chance that the list of values to search will grow beyond a handful, it would be advantageous to use a hash instead, for faster lookups.

Is it likely that you will have different protected and private members on a per-object basis, or would it make more sense to move those definitions outside the constructor?

This is an interesting way to implement objects. I can't see that it's particularly advantageous, but it is interesting.