#!/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';
sub foo {
    local *f = sub {
        my ($n) = @_;
        #f($n); # works, endless recursion.
        #my $f = \&f; # does not work on either v5.14.2 or bleadperl
        my $f = *f{CODE};    # neither does this (both give undef)
        sub {
            if ($n > 0) {
                $n + &{ &$f($n - 1) }
            } else {
                0
            }
        }
    };
    f(@_);
}
my $res = &{ foo 2 };
print $res, "\n";