https://github.com/eserte/perl-tk/commit/3a13aed7a07cd82347695b9595234f629803aef3

--- Tk-804.036/Tk/Pane.pm.orig
+++ Tk-804.036/Tk/Pane.pm
@@ -294,7 +294,7 @@
 
 	my $gridded = $pan->{Configure}{'-gridded'} || '';
 	my $do_gridded = ($gridded eq 'both'
-				|| (!$horz == ($gridded ne 'x'))) ? 1 : 0;
+				|| ((!$horz) == ($gridded ne 'x'))) ? 1 : 0;
 
 	if($do_gridded && $mul eq 'pages') {
 	    my $ch = ($slv->children)[0];