diff --git a/example/retro-unu.forth b/example/retro-unu.forth
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+++ b/example/retro-unu.forth
@@ -0,0 +1,22 @@
+#!/usr/bin/env retro
+
+~~~
+{{
+  'Fenced var
+  :toggle-fence @Fenced not !Fenced ;
+  :fenced? (-f) @Fenced ;
+  :handle-line (s-)
+    fenced? [ over call ] [ drop ] choose ;
+---reveal---
+  :unu (sq-)
+    swap [ dup '~~~ s:eq?
+           [ drop toggle-fence ]
+           [ handle-line       ] choose
+         ] file:for-each-line drop ;
+}}
+~~~
+
+~~~
+#0 sys:argv [ s:put nl ] unu
+~~~
+