That'd be even worse. Now I have yet another variable to deal with when tracking down performance issues in my code. One that would be non-obvious to anyone not

That'd be even worse. Now I have yet another variable to deal with when tracking down performance issues in my code. One that would be non-obvious to anyone not terribly familiar with how things are working behind the scenes. Better would be to introduce a methods that explicitly exposes the type of substring method being used.