Programming Perl, 4th Edition

Accessing Overridden Methods

When a class defines a method, that subroutine overrides methods of the same name in any base classes. You have the Mule object (which is derived from class Horse and class Donkey), and you decide to invoke your object’s breed method. Although the parent classes have their own breed methods, the designer of the Mule class overrode those by supplying the Mule class with its own breed method. That means the following cross is unlikely to be productive:

$stallion = Horse–>new(gender => "male");
$molly = Mule–>new(gender => "female");
$colt = $molly–>breed($stallion);

Now, suppose that through the miracle of genetic engineering, you find some way around a mule’s notorious sterility problem, so you want to skip over the nonviable Mule::breed method. You could call your method as an ordinary subroutine, being sure to pass the invocant explicitly:

$colt = Horse::breed($molly, $stallion);

However, this sidesteps inheritance, which is nearly always the wrong thing to do. It’s perfectly imaginable that no Horse::breed subroutine exists because both Horses and Donkeys derive that behavior from a common parent class called Equine. If, on the other hand, you want to specify that Perl should start searching for a method in a particular class, just use ordinary method invocation but qualify the method name with the class:

$colt = $molly–>Horse::breed($stallion);

Occasionally, you’ll want a method in a derived class to act as a wrapper around some method in a base class. ...