--- ./m4/ax_lua.m4.orig
+++ ./m4/ax_lua.m4
@@ -481,7 +481,7 @@
             ],
             [ ax_cv_lua_header_version=`./conftest$EXEEXT p | \
                 sed "s|^Lua \(.*\)|\1|" | \
-                grep -o "^@<:@0-9@:>@\+\\.@<:@0-9@:>@\+"`
+                grep -E -o "^@<:@0-9@:>@+\\.@<:@0-9@:>@+"`
             ],
             [ax_cv_lua_header_version='unknown'])
           CPPFLAGS=$_ax_lua_saved_cppflags