diff --git a/helm/hpcc/docs/expert.md b/helm/hpcc/docs/expert.md
index a42fc346ba5..5d2249072e2 100644
--- a/helm/hpcc/docs/expert.md
+++ b/helm/hpcc/docs/expert.md
@@ -13,6 +13,8 @@ global:
       time: 200
       interval: 75
       probes: 9
+    regex:
+      cacheSize: 500
 ```
 
 NB: Some components (e.g. DfuServer and Thor) also have an 'expert' settings area (see values schema) that can be used for relavent settings
@@ -73,6 +75,13 @@ service via remote file reads with the ~remote:: syntax.
 Setting expert.allowForeign to true, enables foreign access for compatibility with legacy bare-metal environments
 that have their Dali and Dafilesrv's open.
 
+## regex (cacheSize: unsigned)
+
+See the regex example above.  If set, this should be added at the global level.
+The default value is 500.  Set to zero to disable the cache.
+This value is applied at the process level:  Each Thor worker, Roxie process, and hthor worker receives
+its own cache.  Threads/channels within a process share that process's cache.
+
 
 # Plane Expert Settings