package Circle;

my $PI = 3.1415926;

sub new {
    my $class = shift;
    my ($radius) = @_;

    return bless {
        radius => $radius
    }, $class;
}

sub radius {
    my $self = shift;
    return $self->{radius};
}

sub area {
    my $self = shift;
    return $PI * $self->radius ** 2;
}

sub stretch {
    my $self = shift;
    my ($amount) = @_;

    $self->{radius} += $amount;

    return;
}

##</code><code>##

class Circle
    attr_reader :radius

    @@PI = 3.1415926
    @@PI.freeze

    def initialize ( r = 5 )
        @radius = r
    end

    def area
        @@PI * @radius * @radius
    end

    def stretch ( amount = 1 )
        @radius += amount
    end
end