$mw->after(1, sub {&startup()});
  MainLoop;

##</code><code>##

#!/usr/bin/perl
use warnings;
use strict;
use Tk;

my $mw = tkinit;

my $textbox = &do_Toplevel();

#to wait until a $widget is visible, use waitVisibility: 
$mw->waitVisibility;

#your long startup code, telling it which textbox to display in  
#&startup($textbox); 
&startup1($textbox);

MainLoop;
################################################################# 
sub do_Toplevel {
    my $tl = $mw->Toplevel();
    $tl->title( "Early Status" );
    my $text = $tl->Scrolled('Text')->pack();
    $text->insert('end',"........startup messages.........\n");

    $tl->Button( -text    => "Close",
                 -command => sub { $tl->withdraw }
                )->pack;

 return $text;
}
##############################################################  
sub startup{
  my $textbox = shift;

  foreach my $num (1..10){
        $textbox->insert('end',"$num\n");
        $textbox->update;
        sleep 1;
        }
}

################################################################## 
sub startup1{
  my $textbox = shift;
  $|++;

  tie *STDOUT, 'Tk::Text', $textbox;

 #may need this to force repeated updates 
 # $mw->repeat(10,sub{  $textbox->update }); 


  foreach my $num (1..10){
        print "$num\n";   # printing to STDOUT 
        $textbox->update;
        sleep 1;
        }



}
__END__