Index: java/org/apache/catalina/valves/rewrite/Substitution.java
===================================================================
--- java/org/apache/catalina/valves/rewrite/Substitution.java	(revision 1675545)
+++ java/org/apache/catalina/valves/rewrite/Substitution.java	(working copy)
@@ -89,9 +89,10 @@
         public RewriteMap map = null;
         public String key;
         public String defaultValue = null;
+        public int n;
         @Override
         public String evaluate(Matcher rule, Matcher cond, Resolver resolver) {
-            String result = map.lookup(key);
+            String result = map.lookup(rule.group(n));
             if (result == null) {
                 result = defaultValue;
             }
@@ -162,6 +163,9 @@
                     } else {
                         newElement.key = sub.substring(colon + 1, close);
                     }
+                    if (newElement.key.startsWith("$")) {
+                        newElement.n = Character.digit(newElement.key.charAt(1), 10);
+                    }
                     pos = close + 1;
                     elements.add(newElement);
                 }