Hi, it may help to know that the calling widget is the first argument $_[0] pass to any Tk callback. This code may show you what is happening. Notice how the Entry widget changes with each Tab.

#!/usr/bin/perl

use strict;
use warnings;
use Tk;

my $mw = MainWindow->new();
my $entry1 = $mw->Entry()->pack();
my $entry2 = $mw->Entry()->pack();
my $entry3 = $mw->Entry()->pack();

my %after = ($entry1 => $entry2,
             $entry2 => $entry1,
          );

$mw -> bind('all','<Tab>',sub{ 
                  print "@_\n";
                ($after{$_[0]} // $_[0])->focus;
            }
            );

$mw->MainLoop();
exit(0);
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