> (Would this cause problems? The line should be initialized
> when creating the environment, so not setting it to zero
> in copy should not cause anything to be undefined, no?)
Hmmm, it's more complicated... if we already have a partially
collected line, and the line length changes because of .evc,
what should we do? Make .evc always cause a break, and flush
the partial line before copying the other environment?
Perhaps the current solution of simply clearing the line is
the most pragmatic, because users can always flush an existing
partial line themselves before invoking .evc.