I have trouble understanding your example, but here is how to do correct packForgetting. Notice, you reuse your widgets, NOT make new ones. While they are in a packForget state, you can reconfigure them, then repack them.

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


my $count = 0;

my $top = new MainWindow;
my $txt = $top->Scrolled("Text")->pack;
$txt->insert('end',"Original stuff\n");

my $button1 = $top->Button(-text => "packForget",
          -command => sub{
               my @w = $top->packSlaves;
              foreach (@w) { $_->packForget; }
                  
          &rebuild;                
        })->pack();

my $button = $top->Button(-text => "Exit",
         -command => sub {exit})->pack;

MainLoop;

sub rebuild{
  $txt->delete('0.0','end');
  $txt->insert('end',time."New stuff\n");
  $txt->pack;

$count++;
$button1->configure(-text=>'packForget'.$count); 

$button1->pack;
$button->pack;  

}
 
__END__
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