#!/usr/bin/perl -wT
############################################################################
package P1;
sub new() {
	warn __PACKAGE__;
	my $this = shift(@_);	# Invocand package name.
	my $class = ref($this) || $this;
	my $self = {};
	bless($self, $class);
	$self->initialize({@_});
	return($self);
}
sub initialize($) { my $self = shift(@_); $self->{counter}++; };
############################################################################
package P2;
our @ISA = ('P1');
sub new() {
	warn __PACKAGE__;
	my $this = shift(@_);	# Invocand package name.
	my $class = ref($this) || $this;
	my $self = {};
	bless($self, $class);
	$self->SUPER::initialize({@_});
	$self->initialize({@_});
	return($self);
}
sub initialize($) { my $self = shift(@_); $self->{counter}++; };
############################################################################
package P3;
our @ISA = ('P2');
sub new() {
	warn __PACKAGE__;
	my $this = shift(@_);	# Invocand package name.
	my $class = ref($this) || $this;
	my $self = {};
	bless($self, $class);
	$self->SUPER::initialize({@_});
	$self->initialize({@_});
	return($self);
}
sub initialize($) { my $self = shift(@_); $self->{counter}++; };
############################################################################
package main;
printf "Depth: %d of 3\n", P3->new()->{counter};
############################################################################
1; # Don't forget to return a true value from the file.