mirod wrote: If I use a Null Object I cannot write if( $elt->first_child) {...} anymore.

Ovid begs to differ :)

package Null::Object;

use overload 'bool' => \&bool;
my $self;

sub new { 
    $self ||= bless {}, shift
}

sub AUTOLOAD { $self }

sub bool {
    return;
}

package main;

my $null = Null::Object->new;
$null->foo->bar->baz;

if ($null) {
    print "We shouldn't be here!";
}
else {
    print "We are false!";
}
[download]

That might need a bit of tuning, but you get the idea.

Update: I just noticed that you mentioned overload, so my bit of code is not news to you :) On the other hand, if clean null objects is the only benefit of autoboxing, then I again can't see much of a benefit to them. I might also add that null objects should be the exception rather than the rule, thus the performance impact should be minimal (I hope).

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