The AUTOLOAD function in Newt.pm looks at strerror(errno) to see
whether the constant() function (in Newt.xs) has returned EINVAL.

strerror(errno) is returned in the locale's language, so won't
always match /Invalid/.  constant() should never fail with
EINVAL anyway, so just ignore this case.

--- Newt-1.08/Newt.pm.lang	2003-07-31 12:01:52.000000000 +0100
+++ Newt-1.08/Newt.pm	2003-07-31 12:02:26.000000000 +0100
@@ -220,13 +220,8 @@
   croak "& not defined" if $constname eq 'constant';
   my $val = constant($constname, @_ ? $_[0] : 0);
   if ($! != 0) {
-    if ($! =~ /Invalid/) {
       $AutoLoader::AUTOLOAD = $AUTOLOAD;
       goto &AutoLoader::AUTOLOAD;
-    }
-    else {
-      croak "Your vendor has not defined Newt macro $constname";
-    }
   }
   *$AUTOLOAD = sub { $val };
   goto &$AUTOLOAD;