> When using advanced variable extraction I am unable
> to get the notfound field to work.

This is a bug; fixed for the next (pre)release, thanks for the report!

Besides, the documentation is bogus ; the last field is the "not found" one:
%[param:before:after:empty:notfound]

Here's the patch:

--- htsname.c.orig      2005-10-21 12:05:49.290881626 +0200
+++ htsname.c   2005-10-21 12:01:22.000000000 +0200
@@ -799,6 +799,9 @@
                   strcpybuff(b, name[4]);    /* not found replacement if any
*/
                   b += strlen(b);
                 }
+                                                       } else {
+                                                               strcpybuff(b,
name[4]);    /* not found replacement if any */
+                                                               b +=
strlen(b);
               }
             }
           break;