Understanding code blocks and variable scoping

In the previous chapter, we discussed variables, which are named entities that you use in a program. As in many programming languages, in Perl 6, the names are visible inside their scope and not outside of it.

Take, for instance, a simple program, where the $name variable is only used once, as follows:

my $name = 'Mark';
say "Hello, $name!";

The variable can be reused after it is used in printing the greeting:

my $name = 'Mark';
say "Hello, $name!";

$name = 'Carl';
say "Hello, $name!";

This works because both the printing statements are located in the same scope and the $name variable is visible there.

A block in Perl 6 is a piece of code that is located inside a pair of curly braces. A block creates its own scope. Thus, a variable declared in a block is only visible inside it.

The following program will not compile:

{
    my $name = 'Mark';
    say "Hello, $name!";
}

$name = 'Carl'; # Error here
say "Hello, $name!";

The following error message informs...