Review

package Person;
sub new {
    my $class = shift;
    return bless {}, $class;
}
sub firstName {
    my ( $self, $firstName ) = @_;
    $self->{ firstName } = $firstName if defined $firstName;
    return $self->{ firstName };
}
sub lastName {
    my ( $self, $lastName ) = @_;
    $self->{ lastName } = $lastName if defined $lastName;
    return $self->{ lastName };
}
sub fullName {
    my $self = shift;
    return $self->firstName() . " " . $self->lastName();
}