title: Replace percent-escaped characters in string (%20, %5B, …) with bash
body: <p>I have strings containing percent-escaped characters like <code>%20</code> and <code>%5B</code>, and I would like to transform it to "normal" characters like <code>\</code> for <code>%20</code> and <code>[</code> for <code>%5B</code>.</p>
  
  <p>How can I do that?</p>