diff --git a/extra/peg/peg.factor b/extra/peg/peg.factor
index 8940fc87c6..247d52a19c 100644
--- a/extra/peg/peg.factor
+++ b/extra/peg/peg.factor
@@ -12,6 +12,10 @@ GENERIC: (parse) ( state parser -- result )
 
 SYMBOL: packrat-cache
 SYMBOL: ignore 
+SYMBOL: not-in-cache
+
+: not-in-cache? ( result -- ? )
+  not-in-cache = ;
 
 : <parse-result> ( remaining ast -- parse-result )
   parse-result construct-boa ;
@@ -30,7 +34,9 @@ TUPLE: parser id ;
   dup slice? [ slice-from ] [ drop 0 ] if ;
 
 : get-cached ( input parser -- result )
-  [ from ] dip parser-id packrat-cache get at at ;
+  [ from ] dip parser-id packrat-cache get at at* [ 
+    drop not-in-cache 
+  ] unless ;
 
 : put-cached ( result input parser -- )
   parser-id dup packrat-cache get at [ 
@@ -44,9 +50,13 @@ PRIVATE>
 
 : parse ( input parser -- result )
   packrat-cache get [
-    2dup get-cached [
-      [ (parse) dup ] 2keep put-cached
-    ] unless* 
+    2dup get-cached dup not-in-cache? [ 
+!      "cache missed: " write over parser-id number>string write " - " write nl ! pick .
+      drop [ (parse) dup ] 2keep put-cached
+    ] [ 
+!      "cache hit: " write over parser-id number>string write " - " write nl ! pick . 
+      2nip
+    ] if
   ] [
     (parse)
   ] if ;
diff --git a/extra/peg/pl0/pl0.factor b/extra/peg/pl0/pl0.factor
index b37009238d..b6b030f56c 100644
--- a/extra/peg/pl0/pl0.factor
+++ b/extra/peg/pl0/pl0.factor
@@ -1,15 +1,15 @@
 ! Copyright (C) 2007 Chris Double.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: kernel arrays strings math.parser sequences peg peg.ebnf ;
+USING: kernel arrays strings math.parser sequences peg peg.ebnf memoize ;
 IN: peg.pl0
 
 #! Grammar for PL/0 based on http://en.wikipedia.org/wiki/PL/0
-: ident ( -- parser )
+MEMO: ident ( -- parser )
   CHAR: a CHAR: z range 
   CHAR: A CHAR: Z range 2array choice repeat1 
   [ >string ] action ;
 
-: number ( -- parser )
+MEMO: number ( -- parser )
   CHAR: 0 CHAR: 9 range repeat1 [ string>number ] action ;
 
 <EBNF