package Guestbook;
use base 'CGI::Application';
use strict;

# define all run modes here to allow different sets,
# the actual access control should then be enforced using
# multiple instance scripts, which in turn are placed in a
# secure area and only enable the desired set(s)
sub _RUN_MODES {
          DEFAULT => {
                       view  => 'view_entries',
                       sign  => 'sign_guestbook'
                    },
          RESTRICTED => {
                       delete => 'delete_entry'
                    }
}          

sub enable_rm_set {
     my $self = shift;
     my %run_modes = _RUN_MODES;

     foreach (@_) {
          $self->run_modes( %{$run_modes{$_}} );
          #ensure that info on loaded sets is avaible
          $self->param($_ => '1');
     }
}

sub setup {
     my $self = shift;

     $self->enable_rm_set('DEFAULT');
     $self->start_mode('view');

}

sub view_entries {
    my $self = shift;

    my ($ip, $del_link);
    # are we in "admin mode"?
    if ($self->param('RESTRICTED')) {
        $ip = "with IP's";
        $del_link = '<a href="?rm=delete">+ del option</a>';
    }     

    return "showing guesbook entries $ip";
}

sub sign_guestbook {
     my $self = shift;

     return "sign guestbook";
}

# restricted
sub delete_entry {
     my $self = shift;

     # bail out if authentification did not happen
     # (of course this check should be during setup ;)
     return _no_auth() unless defined($ENV{UserName});

     return "delete entry";
}

sub _no_auth {
     return "oops, authentification did not happen";
}

1;
[download]

use Guestbook;
my $gb = Guestbook->new();

# enable admin mode
$gb->enable_rm_set('RESTRICTED');

$gb->run();
[download]

use Guestbook;
my $gb = Guestbook->new();
$gb->run();
[download]