Sorry about the confusion about protected and private. I've came up (thanks to the replies) with the following 'system' to use.

package Base;

# Base class to experiment with private and protected methods

use warnings;
use strict;
use Carp;

sub new {
        my $type = shift;
        my $class = ref $type || $type;
        my $self = {
                TEXT => undef,
                SECRET => undef,
                NOTSOSECRET => undef,
        };
        my $closure = sub {
                my $field = shift;
                if (@_) { $self->{$field} = shift; }
                return $self->{$field};
        };
        bless ($closure,$class);
        return $closure;
}

# a public accessor to set TEXT
sub text { &{ $_[0] }("TEXT", @_[1 .. $#_]) }

# a private accessor to set SECRET
sub private {
        caller(0) eq __PACKAGE__ || confess "private method";
        &{ $_[0] }("SECRET", @_[1 .. $#_]); 
}

# a public accessor to set SECRET by means of the private method
sub secret {
        private($_[0],@_[1 .. $#_]);
}

# a protected accessor to set NOTSOSECRET
sub protected {
        caller(0)->isa(__PACKAGE__) || confess "protected method\n";
        &{ $_[0] }("NOTSOSECRET", @_[1 .. $#_]); 
}

1;
[download]

package Inherit;

# Inherit class to experiment with private and protected methods

use warnings;
use strict;

use Base;
use vars qw(@ISA);
@ISA = qw(Base);

sub inheritSecret {
        $_[0]->private(@_[1 .. $#_]);
}

sub inheritNotSoSecret {
        $_[0]->protected(@_[1 .. $#_]);
}

1;
[download]

The main routine that calls all:

#!/usr/bin/perl

use warnings;
use strict;
use Base;
use Inherit;

my $base = Base->new();
$base->text("hello");
print $base->text . "\n";

my $inherit = Inherit->new();
$inherit->text("howdy");
print $inherit->text . "\n";

$base->secret("secret");
print $base->secret . "\n";

# this will get us an error saying private method
#$inherit->inheritSecret("verySecret");
#print $inherit->inheritSecret . "\n";

# impossible to access protected directly
#$inherit->protected("notsosecret");
#print $inherit->protected . "\n";

# access to NOTSOSECRET by means of a protected method
$inherit->inheritNotSoSecret("notsosecret");
print $inherit->inheritNotSoSecret . "\n";
[download]

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