Hi,
the bug you describe seems to appear on windows only. It can be boiled down to the following example.
Also this workaround is a bit more 'general-purpose' as it does not require the widget to be managed by the 'pack' geometry manager:
use strict;
use warnings;
use Tk;
use Tk::Text;
my $mw = tkinit;
my $t = $mw->Scrolled('Text',
-scrollbars => 'osoe',
)->pack;
$t->update;
$t->insert("insert", sprintf "%3d. Text Text Text\n",$_) for(0..64);
$t->update;
# force scrollbar refresh:
# my $sb = $t->Subwidget('yscrollbar');
# $sb->set( $sb->get );
MainLoop;
Cheers, Christoph