title: How to iterate through Hash (of Hashes) in Perl?
body: <p>I have Hash where values of keys are other Hashes.</p>
  
  <p>Example: <code>{'key' =&gt; {'key2' =&gt; {'key3' =&gt; 'value'}}}</code></p>
  
  <p>How can I iterate through this structure?</p>