Variable "$entry" will not stay shared at C:\community\toplevel.pl line 32.
Variable "$window2" will not stay shared at C:\community\toplevel.pl line 33.
Global symbol "$variable" requires explicit package name at C:\community\toplevel.pl line 22.
Global symbol "$variable" requires explicit package name at C:\community\toplevel.pl line 34.
Execution of C:\community\toplevel.pl aborted due to compilation errors.

#!/usr/bin/perl

use strict;
use warnings;
use Tk;
use Tk::HList;
use Tk::ItemStyle;

my $variable;
my $fenster = new MainWindow;
my $hl = $fenster->HList(-width => 50,)->pack();
my $style = $hl->ItemStyle('text',
                          -foreground => '#FF0000',
                          -selectforeground => '#FF0000'
                          );

my $toplevel = $fenster->toplevel;
my $menubar = $toplevel->Menu(-type => 'menubar');
$toplevel->configure(-menu => $menubar);
my $datei = $menubar->cascade(-label => '~Datei',
                             -tearoff => 0);
$datei->command(-label => 'Zeige', -command => sub{nickchange()});
$datei->command(-label => 'Quit', -command => [$fenster=>'destroy']);

$hl->repeat(1000, sub{print $variable;});

MainLoop;

sub nickchange {
   my $window2 = $fenster->Toplevel;
   my $text = $window2->Label(-text => "Nickname eingeben")->pack();
   my $entry = $window2->Entry()->pack();
   my $button = $window2->Button(-text => 'Ok',-command => [\&action,$window2,$entry])->pack();
}


sub action {
    my ($window2,$entry) = @_;
    my $eingabe = $entry->get();
    $window2->destroy();
    $variable = $eingabe;
}