... and while we are at it, I noticed a different small issue with the article.

Towards the end, in the subs to_string and to_num it reads

sub to_string {
    my $self = shift;
    return "$_->{num}/$_->{den}";
}

sub to_num {
    my $self = shift;
    return $_{num}/$_->{den};
[download]

while that should be (as it is in the cpan version 1.02)

sub to_string {
  my $self = shift;

  return "$self->{num}/$self->{den}";
}

sub to_num {
  my $self = shift;

  return $self->{num} / $self->{den};
}
[download]

-- Hofmator