Here is a simple example of using inheritance:

Say you have some stock footage for an action-adventure TV show, and you want to re-use it several times without anyone noticing. This week, we are going to flip a jeep and distract some guards.

use strict;
use ordnance;
 
my $T= new ordnance();
$T->flip_jeep(); sleep 2;
$T->firecracker();
[download]

This week's episode uses the ordnance module, which inherits from the stock_footage module.

Here is ordnance.pm:

package ordnance;
use stock_footage;
 
@ISA=qw(stock_footage);
 
sub new
{
  my $this = shift;
  my $class = ref($this) || $this;
  my $self = {};
  bless $self, 'ordnance';
}
 
sub flip_jeep
{
  my $this = shift;
  my $class = ref($this) || $this;
  print "pull grenade pin\n"; sleep 2;
  $class->SUPER::flip_jeep();
}
 
sub firecracker
{
  my $this = shift;
  my $class = ref($this) || $this;
  print "light fuse\npsssss....\n"; sleep 2;
  print "Bang! Bang! Bang!\n";
  $class->SUPER::distraction();
}
 
1;
[download]

and here is stock_footage.pm:

package stock_footage;
 
sub flip_jeep
{
  print "And the jeep flies into the air and flips!\n";
}
 
sub distraction
{
  print "And the guards are momentarily distracted!\n";
}
[download]

So, someone can write this week's show using my ordnance routines, and they won't know that they are actually using stock_footage. Of course, I would write pod documentation for my ordnance routines so that the caller doesn't have to look at the ordnance code to know how to use it.

I have not written much code that uses inheritance, but I'm sure that other monks can correct me if I have messed up my code. There are many things you can do with inheritance, just as there are many things you can do with a for loop. I would like an even more brief example, if someone can figure one out.

UPDATE:Fixed problems pointed out by tilly and petdance.

It should work perfectly the first time! - toma