How do I decode an encoded URL?

This question has been asked frequently (and variants of 'decode' keep showing up in this site's search logs). While the Server object provides a Server.URLEncode() method, they didn't bother providing a Server.URLDecode() or Server.URLUnEncode() method. I assume they didn't think it would ever be needed, but they were wrong... I've been in a few situations where this function would have been very handy. Here are both URLEncode and URLDecode functions (for completeness) in VBScript and JScript: 
 
In VBScript: 
 

<%      Function URLDecode(str)          str = Replace(str, "+", " ")          For i = 1 To Len(str)              sT = Mid(str, i, 1)              If sT = "%" Then                  If i+2 < Len(str) Then                      sR = sR & _                          Chr(CLng("&H" & Mid(str, i+1, 2)))                      i = i+2                  End If              Else                  sR = sR & sT              End If          Next          URLDecode = sR      End Function        Function URLEncode(str)          URLEncode = Server.URLEncode(str)      End Function        str1 = "http://www.foo.com/blah.asp?foo=1 & 2 &g=0"      str2 = URLEncode(str1)      str3 = URLDecode(str2)      Response.Write(str1 & "<br>" & str2 & "<br>" & str3)  %>

 
And here in JScript: 
 

<script language=JScript runat=server>        function URLDecode(str)      {          return unescape(str);      }        function URLEncode(str)      {          str = escape(str);            // JScript doesn't think '/' needs to be escaped...          // I'm not sure it does either, but take it out to be          // consistent with VBScript's built-in URLEncode()            while (str.indexOf("/")!=-1)          {              str = str.replace("/","%2F");          }          return str;      }        var str1 = "http://www.foo.com/blah.asp?foo=1 & 2 &g=0";      var str2 = URLEncode(str1);      var str3 = URLDecode(str2);      Response.Write(str1 + "<br>" + str2 + "<br>" + str3)    </script>