Use improved sed expression, proposed by Thien-Thi Nguyen.

 dnl This file is part of GNU mailutils.
-dnl Copyright (C) 2001 Free Software Foundation, Inc.
+dnl Copyright (C) 2001, 2006 Free Software Foundation, Inc.
 dnl
 dnl This program is free software; you can redistribute it and/or modify
 dnl it under the terms of the GNU General Public License as published by
@@ -46,7 +46,7 @@ AC_DEFUN([MU_CHECK_GUILE],
 
    if test $GUILE_CONFIG != no; then
      AC_MSG_CHECKING(for guile version 1.4 or higher)
-     GUILE_VERSION=`($GUILE_CONFIG --version 2>&1; echo '')|sed -n 's/guile-config - Guile version \([[0-9]][[0-9]]*\)\.\([[0-9]][[0-9]]*\).*/\1\2/p'`
+     GUILE_VERSION=`($GUILE_CONFIG --version 2>&1; echo '')|sed -n 's/guile-config [[^0-9]]* \([[0-9]][[0-9]]*\)\.\([[0-9]][[0-9]]*\).*/\1\2/p'`
      case "x$GUILE_VERSION" in
      x[[0-9]]*)
        if test $GUILE_VERSION -lt 14; then