And here's a ListBox2 with three subwidgets.

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11118320
use warnings;
use Tk;

{ # for package
package Tk::ListBox2;

use base qw/ Tk::Frame /;     # Frame-based composite
Construct Tk::Widget 'ListBox2'; # install MyNewWidget in pTk namespac
+e

sub ClassInit                  # called once to initialize new class
  {
  my($class, $mw) = @_;
  $class->SUPER::ClassInit($mw);
  }

sub Populate                # called to build each widget instance
  {
  my($self, $args) = @_;
  $self->SUPER::Populate($args);

  my $outer = $self->Frame()->pack(-fill=> 'both', -expand=> 1);
  $outer->Label(-text => 'A ListBox2', -fg => 'blue')->pack;
  my $inner = $outer->Listbox()->pack(-fill=> 'both', -expand=> 1);
  $outer->Label(-text => 'End of ListBox2', -fg => 'blue')->pack;

  $self->ConfigSpecs( DEFAULT => [$inner] );

  $self->Delegates(
    Construct => $inner,
    insert => $inner,
    );
  }
} # end package

my $mw = MainWindow->new;
my $lb = $mw->ListBox2()->pack(-fill => 'both', -expand => 1);
$lb->insert( 'end', 1 .. 10 );

MainLoop;
[download]

since I wasn't sure exactly what you were trying to do...