How do you test code that uses scalars ($)?

# Example of testing Perl code that uses scalars
my $scalar1 = 10;           # A scalar variable
my $scalar2 = 20;           # Another scalar variable

# Subroutine to add two scalars
sub add_scalars {
    my ($a, $b) = @_;      # Receive parameters
    return $a + $b;        # Return the sum
}

# Testing the add_scalars subroutine
my $result = add_scalars($scalar1, $scalar2);
print "The sum of $scalar1 and $scalar2 is: $result\n";  # Expected output: The sum of 10 and 20 is: 30