Think Perl 6

Chapter 2. Variables, Expressions, and Statements

One of the most powerful features of a programming language is the ability to manipulate variables. Broadly speaking, a variable is a name that refers to a value. It might be more accurate to say that a variable is a container that has a name and holds a value.

Assignment Statements

An assignment statement uses the equals sign (=) and gives a value to a variable, but, before you can assign a value to a variable, you first need to create the variable by declaring it (if it does not already exist):

> my $message;          # variable declaration, no value yet
> $message = 'And now for something completely different';
And now for something completely different
> my $number = 42;      # variable declaration and assignment
42
> $number = 17;         # new assignment
17
> my $phi = 1.618033988;
1.618033988
>

This example makes four assignment statements. The first assigns a string to a new variable named $message, the second assigns the integer 42 to $number, the third reassigns the integer 17 to $number, and the fourth assigns the (approximate) value of the golden ratio to $phi.

There are two important syntax features to understand here.

First, in Perl, variable names start with a so-called sigil, i.e., a special non-alphanumeric character such as $, @, %, &, and some others. This special character tells us and the Perl compiler (the program that reads the code of our program and transforms it into computer instructions) which kind of variable it is. For example, ...