Overloading in Perl / Using overload.pm

Number Fraction::add (version 2)

• sub add {
    my ($l, $r) = @_;
    if (ref $r) {
      if (UNIVERSAL::isa($r, ref $l) {
        return 
          Number::Fraction->new($l->{num} 
                              * $r->{den} 
                              + $r->{num} 
                              * $l->{den},
                                $l->{den} 
                              * $r->{den})
      } else {
        ...
      }
    else {
      ...
    }
  }