#!/usr/bin/env perl

# Copyright (c) 2015 Christian Jaeger, copying@christianjaeger.ch
# This is free software. See the file COPYING.md that came bundled
# with this file.

use strict; use warnings; use warnings FATAL => 'uninitialized';

use Scalar::Util "weaken";

sub foo {
    my $f; $f= sub {
        my ($n)= @_;
        my $f=$f; # create a new, strong binding for f to prevent it
                  # from being freed (upon return from f)
        sub {
            if ($n > 0) {
                $n + &{&$f($n - 1)}
            } else {
                0
            }
        }
    };
    my $f_= $f; weaken $f;
    &$f_;
}

my $res= &{foo 2};

print $res,"\n";

