diff -Nuar hol_light/hol.ml hol_light.nixos/hol.ml
--- hol_light/hol.ml	2010-09-12 18:57:28.000000000 +0200
+++ hol_light.nixos/hol.ml	2010-09-12 19:09:09.000000000 +0200
@@ -11,8 +11,8 @@
 
 let hol_version = "2.20++";;
 
-let hol_dir = ref
-  (try Sys.getenv "HOLLIGHT_DIR" with Not_found -> Sys.getcwd());;
+let hol_dir = ref "@HOL_LIGHT_SRC_DIR@";;
+Topdirs.dir_directory "@HOL_LIGHT_SRC_DIR@";;
 
 (* ------------------------------------------------------------------------- *)
 (* Should eventually change to "ref(Filename.temp_dir_name)".                *)
@@ -23,20 +23,6 @@
 let temp_path = ref "/tmp";;
 
 (* ------------------------------------------------------------------------- *)
-(* Load in parsing extensions.                                               *)
-(* For Ocaml < 3.10, use the built-in camlp4                                 *)
-(* and for Ocaml >= 3.10, use camlp5 instead.                                *)
-(* ------------------------------------------------------------------------- *)
-
-if let v = String.sub Sys.ocaml_version 0 4 in
-   v = "3.10" or v = "3.11"
-then (Topdirs.dir_directory "+camlp5";
-      Topdirs.dir_load Format.std_formatter "camlp5o.cma")
-else (Topdirs.dir_load Format.std_formatter "camlp4o.cma");;
-
-Topdirs.dir_load Format.std_formatter (Filename.concat (!hol_dir) "pa_j.cmo");;
-
-(* ------------------------------------------------------------------------- *)
 (* Load files from system and/or user-settable directories.                  *)
 (* Paths map initial "$/" to !hol_dir dynamically; use $$ to get the actual  *)
 (* $ character at the start of a directory.                                  *)