title: awk gsub using variable for pattern matching
body: <p><code>gsub(<strong><em>pattern</em></strong>, <em>replacement</em>, <em>target</em>)</code>: allows a variable to be used for <strong><em>pattern</em></strong>, but does not let me do regular expression.</p>
  
  <p><code>gsub(<strong>/<em>pattern</em>/</strong>, <em>replacement</em>, <em>target</em>)</code>: lets me do regular expression, but I cannot use a variable for the <strong><em><code>pattern</code></em></strong>.</p>
  
  <p>Is there a way to get both variable pattern and regex to work in <code>gsub</code>? I'd like to stick with awk, no sed or shell.</p>