Make "range" one smaller (discrepancy between doc and source for regex.c!).
diff --git a/Modules/regexmodule.c b/Modules/regexmodule.c
index 97578a0..1fb3573 100644
--- a/Modules/regexmodule.c
+++ b/Modules/regexmodule.c
@@ -134,7 +134,7 @@
 		err_setstr(RegexError, "search offset out of range");
 		return NULL;
 	}
-	range = size - offset + 1;
+	range = size - offset;
 	re->re_regs_valid = 0;
 	result = re_search(&re->re_patbuf, buffer, size, offset, range,
 			   &re->re_regs);