package Objet; # yes, the 'c' is absent by design;
use strict;
use warnings;

sub new {
   my $self = bless {}, shift;
   my %args = @_;
   while (my $k, $v = each %args) {
      $self->attrib($k => $v);
   }
   return $self;
}

sub attrib {
   my $self = shift;
   my ($attr, $value) = @_;

   # if we aren't setting, then get.
   # I don't use defined $value, because setting to undef might be ok.
   return $self->{$attr} unless (scalar @_ >= 2); 

   # otherwise, set the attribute
   $self->{$attr} = $value;
}

1;

##</code><code>##

use Objet;
my $o = Objet->new('aleph' => 1, 'gamma' => 2);

$o->attrib( 'zeta' => 900 ); # sets attribute 'zeta' to 900
print $o->attrib( 'aleph' ); # gets value of attrib 'aleph'

##</code><code>##

sub new {
   my $self = bless {
     alpha => {
       value  => undef,
       set_ok => 1,
       get_ok => 1,
       set    => sub {
         # untested.
         my $self = shift;
         $self->_set_alpha(@_);
       },
       get    => sub {
         my $self = shift;
         $self->{alpha}{value};
       },
       valid  => sub {
         my $val = shift;
         return ($val =~ m/^\d+$/) ? 1 : 0; #only digits
       },
     },
   }, shift;

   return $self;
}   

sub attrib {
   my $self = shift;
   my ($attr, $value) = @_;
   
   die("No attribute '$attr'")
     unless (ref $self->{$attr} eq 'HASH');

   # set
   if (scalar @_ >= 2) {
      die("Not allowed to set '$attr'") unless $self->{$attr}{set_ok};
      die("Invalid value for '$attr'") 
        unless $self->{$attr}{valid}->($value);
      $self->{$attr}{set}->($value);
   }
   else {
      die("Not allowed to get '$attr'") unless $self->{$attr}{get_ok};
      return $self->{$attr}{get}->();
   }
}