As you read in the Introduction, sometimes just making decisions and running code conditionally are not enough. Often you need to run pieces of code over and over again. The exercise presented in Listing 3.1 wasn't much fun because you could take only one guess (well, that and because it's a pointless game). If you want to be able to take multiple guesses, you need to be able to repeat sections of code conditionally, and that's what looping is all about.
Looping with while
The simplest kind of loop is a while loop. A while loop repeats a block of code as long as an expression is true. The syntax for a while loop looks like this:
while (expression) block
When Perl encounters the while statement, it evaluates the expression. If the