Scalars

A scalar is a container that can keep a single value, such as an integer, a string, or an object.

Scalar variables use the $ sigil. We have seen a few examples in the previous sections, and here are some more. Notice that the same scalar variable, if it is not explicitly declared with a data type, can host a value of different types at different moments:

my $x = 42;
say $x;
my $y = $x * 2;
say $y;

$x = 'Hello, World!';
say $x;

(Of course, it is better not to change the type of the data during the program flow.)

Inside the strings in double quotes, scalar variables are interpolated and replaced by their current values. In the following program, the process of calculating an equation is printed as a string:

my $a = 3;
my $b = 4;
my $c = sqrt($a * $a + $b * $b);

say "If the legs of a right triangle are $a and $b, ";
say "then the hypotenuse is $c.";

This code prints the following output:

If the legs of a right triangle are 3 and 4, 
then the hypotenuse is 5.

Now, let's move on to the next type of variables—arrays.