Um, no events are dispatched before MainLoop ... you need this logic 
#!/usr/bin/perl
use strict;
use warnings;
use Tk;

my $mw = MainWindow->new;
$mw->geometry("300x300");

my $topics3 = $mw->Radiobutton(
        -text =>'Selection 3',
        -value => '3',
        -command => sub {
            $mw->Optionmenu( 
                -options => [ 6, 6, 6 ],
            )->pack();
        },
    )->pack();

MainLoop;

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In reply to Re: propper use of bind in perl tk by Anonymous Monk
in thread propper use of bind in perl tk by pashanoid

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