title: Replace Unicode numeral subscript or superscript with plain numeral
body: <p>How do I replace a Unicode numeral subscript or superscript (eg, <code>₂</code>) with the corresponding numeral (ie, <code>2</code>) using regular expressions? I can of course replace each of them separately, but that is ten lines of code... </p>
  
  <p>I am implementing this in Perl but that should not really matter.</p>