title: ZSH: rename files in nested folders, capitalize specific letters
body: <p>I have many nested folders of json language files, such as</p>
  <pre><code>da-dk.json
  de-de.json
  en-us.json
  </code></pre>
  <p>I need to change them all to capitalize the letters after the hyphen, as in</p>
  <pre><code>da-DK.json
  de-DE.json
  en-US.json
  </code></pre>
  <p>I am on a Mac with zsh.  I originally thought I could do it with a GUI utility I have used called A Better Finder Rename but it apparently  does not offer case conversions on replace.</p>
  <p>I know regex and figured it would be something like find
  <code>^([a-z]{2})-([a-z]{2})</code> and replace with <code>$1-\U$2</code> but I'm not sure how to do this in the command line.</p>