Just a note - I found something, that works:
>import std.stdio;
>
>void main(string[] args)
>{
> immutable cond = args[1]=="a";
> if (cond) write("A");
> scope (exit) if (cond) write("B");
>
> write("C");
>}
I'm using the immutable variable to avoid, that the condition
changes later.