Useful alternative control structures?

Question

Sometimes when I am programming, I find that some particular control structure would be very useful to me, but is not directly available in my programming language. I think my

Answer 1

I propose the "then" operator. It returns the left operand on the first iteration and the right operand on all other iterations:

var result = "";
foreach (var item in items) {
    result += "" then ", ";
    result += item;
}

in the first iteration it adds "" to the result in all others it adds ", ", so you get a string that contains each item separated by commas.