#!/usr/bin/perl

# http://perlmonks.org/?node_id=1166034

use strict;
use warnings;
use Tk;

my $mw = new MainWindow( -takefocus => 1 );
$mw->geometry( "300x300" );
my $label = $mw -> Label(-text=>"Hello World",
  -takefocus => 0 ) -> pack();
my $buttonframe = $mw->Frame(
  -relief => 'sunken',
  -padx => 2, -pady => 2,
  -takefocus => 0,
  -bd => 1,
  )->pack();
my $button = $buttonframe -> Button(-text => "Show", 
    -padx => 10, -pady => 6,
    -takefocus => 1,
    -command => sub { showmessage(); })
  -> pack();
$button->focus;
MainLoop;

sub showmessage{
  $mw->messageBox (-message=>"The glossary has been merged", -icon=> '
+info',
  -type => 'YesNoCancel');
}
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Note that the sunken frame is put around the default button in the messageBox, the other buttons are just plain buttons.