1 files changed, 3 insertions, 1 deletions
diff --git a/HACKING b/HACKING
index b837a38cc..f3d60a899 100644
--- a/HACKING
+++ b/HACKING
@@ -57,9 +57,11 @@ libtool 1.4 --- a system for managing the zillion hairy options needed
 	on various systems to produce shared libraries.  Available in
 	"ftp://ftp.gnu.org/pub/gnu/libtool"
 
+flex 2.5.4 --- a tokenizer generator.  earlier versions will most
+        probably work too.
+
 You are lost in a little maze of automatically generated files, all
 different.
->
 
 
 Contributing Your Changes ============================================