#!/usr/bin/perl -w
use strict;
use Tk;

#this leaks 

my $mw = Tk::MainWindow->new( -title => 'Listbox Leak' );

my $lb = $mw->Listbox()->pack();
my $b  = $mw->Button(
    -text    => 'Leak',
    -command => \&leak
)->pack();

MainLoop;

sub leak {
    $lb->delete( 0, 'end' );
    $lb->insert( 'end', 1 .. 10000 );
}