Declaring variables

Every variable must be declared before its use in the program. You don't need to declare all the variables at the beginning of the program. From a practical perspective, the point of declaration can (and should) be as close as possible to the place where it is first used. The most practical reason to do that is to make the visibility of the variable better—if you declare too early, you force the reader of your program to think about the purpose of the variable; on the other hand, if you make changes in the code, there is a big chance of forgetting to remove the variable declaration if it is not located close to the place it is used.

To declare a variable, use the my keyword, as shown here:

my $x;

It is possible to declare a variable together with initialization:

my $x = 42;

Perl 6 also defines the concept of constants. These are variables whose value can only  be set once in the initializer. To create a constant, use the constant keyword, as shown here:

constant $C = 10;