We had a good discussion in Chapter 5, Advanced Expressions, on how to use variables with the Dollar-sign Expansion. Variables are so important to what we do in the script that it is worth just briefly reviewing the topic from a script point of view.

Variables can be assigned in the script using either a Set or Let statement.

A Set statement will assign the text on the right-hand side of the statement to the variable. A Let statement will try and evaluate the text on the right-hand side as an expression and will assign the result of that evaluation (which might be null!) to the variable. For example:

Set v1=1+1;

This will result in the v1 variable that contains the value 1+1. Consider the following example:

Let v2=1+1;

This will result in the v2 variable that contains the value 2.

A variable can be used simply in assignment to other variables. For example:

Let v3=v2+1;

The v3 variable will have the value 3 (2+1). Let's consider another...