The output of Data::Dumper is not guaranteed to properly evaluate and reconstruct the data, unless you set $Data::Dumper::Purity = 1. It is still possible to confuse Data::Dumper in some cases, but with Purity, it'll handle most self-referential and other cyclical structures. The output with this configuration:

$VAR1 = {
          'k1' => {
                    'k11' => [
                               'v1',
                               'v2'
                             ],
                    'k12' => 'w00t!'
                  },
          'k2' => {
                    'k21' => 'what?',
                    'k22' => []
                  }
        };
$VAR1->{'k2'}{'k22'} = $VAR1->{'k1'}{'k11'};
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As you can see, Data::Dumper now produces Perl code, and not merely a Perl-like syntax to describe the data.