#!/usr/bin/perl
use strict;
use warnings;
use Tk;

my $Text = 'Dies ist ein langer Text, der im Label gescrollt wird. ';
my $Mw = MainWindow->new(-title => 'TkTicker');
my $LabelW = $Mw->Label(-textvariable => \$Text)->pack(-expand => 1, -fill => 'x');

$Mw->repeat (100, \&tick);
$Mw->MainLoop;

sub tick {
    my $width = $LabelW->cget('width');
    return unless $width < length $Text;
    $Text = substr($Text,1,length($Text)-1) . substr($Text,0,1);
}