updated for version 7.3.196
Problem:    Can't intercept a character that is going to be inserted.
Solution:   Add the InsertCharPre autocommand event. (Jakson A. Aquino)
diff --git a/runtime/doc/map.txt b/runtime/doc/map.txt
index ec21d15..ceb2901 100644
--- a/runtime/doc/map.txt
+++ b/runtime/doc/map.txt
@@ -226,7 +226,7 @@
 
 For abbreviations |v:char| is set to the character that was typed to trigger
 the abbreviation.  You can use this to decide how to expand the {lhs}.  You
-can't change v:char and you should not insert it.
+you should not either insert or change the v:char.
 
 Be very careful about side effects!  The expression is evaluated while
 obtaining characters, you may very well make the command dysfunctional.