patch 8.0.0020
Problem:    The regexp engines are not reentrant.
Solution:   Add regexec_T and save/restore the state when needed.
diff --git a/runtime/doc/change.txt b/runtime/doc/change.txt
index 51e699b..6dced7b 100644
--- a/runtime/doc/change.txt
+++ b/runtime/doc/change.txt
@@ -1,4 +1,4 @@
-*change.txt*    For Vim version 8.0.  Last change: 2016 Sep 11
+*change.txt*    For Vim version 8.0.  Last change: 2016 Oct 02
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -913,8 +913,7 @@
 Substitute with an expression			*sub-replace-expression*
 						*sub-replace-\=* *s/\=*
 When the substitute string starts with "\=" the remainder is interpreted as an
-expression.  This does not work recursively: a |substitute()| function inside
-the expression cannot use "\=" for the substitute string.
+expression.
 
 The special meaning for characters as mentioned at |sub-replace-special| does
 not apply except for "<CR>".  A <NL> character is used as a line break, you