my $foo = be({name => "foo"});
my $bar = be({name => "bar", data => $foo});
my $baz = be({name => "baz", data => $bar});

sub gotcha {
  $bar->{"bar can't go"} = "until this function is cleaned up";
}

sub be {
  return bless shift;
}

sub DESTROY {
  my $self = shift;
  print "$self->{name} died\n";
}

__END__

on 5.005_03 for me prints:

baz died
foo died
bar died
[download]

You can also just store a reference to your lexical in a global to simulate the same thing. Yes, "global" "closures" are probably harder to notice than global variables, but the same basic principle applies: keeping a reference to something around prevents it from being destroyed (until global destruction, of course).

But none of that changes the fact that you can avoid the problems with misordered destruction by using only lexical (including making sure that any references to said lexicals are also only in lexicals, etc.). That is a very practical bit of information.

Also, current versions of Perl create a reference loop for "real" closures and so they would also cause you problems (as well as leaking memory if you create lots of closures).

        - tye (but my friends call me "Tye")

Yes, you can do the same with a global variable. However my point was that even with every lexical in file scope, having one of the direct references to a lexical inside of a function brings the problem back.

BTW the more I think about it, the more I like the idea of having a flyweight implementation with an END block to kill all of the objects. That allows module authors to create objects which clean themselves up reliably without assuming that users are cautious.