What you can also add is code to watch for the resize event, occuring while the Frames are unpacked. You can keep a running array of the current window size.

It seems to me that repacking your children into larger frames might be accomplished by using -fill=>both -expand=>1 in the packing, and then calling the packPropagate command.... but that is untested.

#!/usr/bin/perl
use warnings;
use strict;
use Tk;
my $mw = new MainWindow;

my $current_size = $mw->reqwidth . "x" . $mw->reqheight;
my $old_current_size = $current_size;

$mw->bind( '<Configure>', sub{ &OnResize });

my $leave = 0;
$mw->bind( '<Leave>',sub { $leave = 1; } );

$mw->bind( '<Enter>',sub { $leave = 0; 
                           &OnResize;
             } );

MainLoop;

sub OnResize {
      
    my $current_size = $mw->width . "x" . $mw->height;
    if( $leave == 1) {return }
    if($old_current_size eq $current_size){return}


     ## Resize has occurred do something:
     printf( "Resize happened - old size: %s, new size: %s\n",
                             $old_current_size, $current_size );
    ## set the old size to the new size
    $old_current_size = $current_size;
}
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