--- tcl8.5.9/library/init.tcl.orig	2012-05-17 05:28:16.038636462 -0700
+++ tcl8.5.9/library/init.tcl	2012-05-17 05:29:58.370740558 -0700
@@ -43,7 +43,16 @@
     if {[info exists env(TCLLIBPATH)]} {
 	set auto_path $env(TCLLIBPATH)
     } else {
-	set auto_path ""
+        # Add in $MACH64 library directory (if needed).
+        if {$tcl_platform(wordSize) == 8} {
+            if {$tcl_platform(machine) eq "i86pc"} {
+                set auto_path "/usr/lib/amd64"
+            } else {
+                set auto_path "/usr/lib/sparcv9"
+            }
+        } else {
+            set auto_path ""
+        }
     }
 }
 namespace eval tcl {