There are, of course, many different ways to create more-advanced and sophisticated scripts, notably including shell script functions, but we'll delve into those as we proceed. I'm a big fan of just ...

Werner Brannath, Peter Bauer, Optimal Conditional Error Functions for the Control of Conditional Power, Biometrics, Vol. 60, No. 3 (Sep., 2004), pp. 715-723 ...