Loops

• while loops
• Basic format:

             while (condition) {
                instructions
                 .
                 .
                 .
              }

• Everything within the curly braces ("{ }") is executed from zero to an infinite number of times.

• Example:

              #!perl

              $x = 0;
              
              while ($x < 10) {
                print "The value of x is: $x\n";
                $x++;
              }

              print "All done.  The value of x is now: $x\n";
                           

• How it works:
• condition is some sort of comparision: for example,  $x < 10 (value of $x less than 10.)
• The condition is tested by the while statement.
  
• When Perl gets to the while,she examines the condition.  "Is the value of variable $x less than 10 right now?" she asks.
• If $x is less than 10 right now, Perl then runs the instructions between the curly braces. 
  
• When Perl sees the closing brace ("}") she goes back up to the while statement.
• If $x is not less than 10 right now (in other words, if it is equal to or greater than 10), Perl skips all of the instructions between the curly braces and executes the next instruction after the closing brace.

• Output of this program:

             The value of x is: 0
             The value of x is: 1
             The value of x is: 2
             The value of x is: 3
             The value of x is: 4
             The value of x is: 5
             The value of x is: 6
             The value of x is: 7
             The value of x is: 8
             The value of x is: 9
             All Done.  The value of x is now: 10

• foreach loops

		print "You must be at least 15 years old...\n";
		@ages = (10, 12, 12, 14, 15, 17, 18);
		
		foreach $age (@ages) {
			print "You're $age... "
			if ($age >= 15) {
				print "that's old enough.\n";
			}
			else {
				print "that's not old enough.\n";
			}
		}