title: Regular Expression to match multiple query string parameter/value pairs
body: <p>About to work through this one, but thought someone may have already had to tackle it, so...</p>
  
  <p>I'm looking for an elegant (and isapi rewrite compatible) regular expression to look for three known parameter/value pairs in a querystring, regardless of order, and also extract all other parameters while stripping out those three.</p>
  
  <p><strong>abc=123</strong> <strong>def=456</strong> and <strong>ghi=789</strong> are all known, fixed strings. They may appear in any order in the querystring, and may or may not be the only parameters, may or may not be adjacent. It should be smart and not match  a<strong>aabc=123</strong> or <strong>abc=123</strong>4 (so each searched parameter should be bracketed by &amp;, ?, #, or end of string).  The output I want is a new query string with the remaining params stripped out.  </p>
  
  <p>I'll probably be taking a stab at the logic in the morning, so bonus points if you can solve it before I try to then.</p>