use Attribute::Handlers;
use Carp;
 
sub private :ATTR(CODE) {
            my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
            my $name = *{$symbol}{NAME};
            *{$symbol} = sub {
                        croak "Function $name is declared private in $package"
                                    if caller ne $package;
                        $referent->(@_)
            }
}

##</code><code>##

package EventHandlers;
 
our %EventHandlers;
 
use Attribute::Handlers;
use Carp;
 
sub Event :ATTR(CODE) {
            my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
            my $name = *{$symbol}{NAME};
            $EventHandlers{$name} = 1;
}

##</code><code>##

package Annotations;
 
my %Annotations;
 
sub Annotate {
            my ($sub, %annotations) = @_;
            bless $sub, Annotations;
            my $h = $Annotations{$sub} ||= {};
            @$h{keys %annotations} = values %annotations;
}
 
sub annotation {
            my ($this, $name) = @_;
            $Annotations{$this}{$name}
}

##</code><code>##

package Events;
 
use Annotations;
use Attribute::Handlers;
 
sub Event :ATTR(CODE) {
            my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
            Annotations::Annotate($referent, eventhandler => 1);
}

##</code><code>##

if (my $event = MyEvents->can($CGI->param('event'))) {
            die unless $event->annotation('eventhandler');
            MyEvents->$event();
}

##</code><code>##

$event->{eventhandler}

##</code><code>##

annotation($event, 'eventhandler')