Please don't use code takes where they are not needed (again read and understand How do I post a question effectively? and PerlMonks for the Absolute Beginner). If you use Super Search you can find some examples of scrolling content/marquees in Tk such as Re: News alerts using the BBC's news ticker data file among others.

use strict;
use warnings;
use Tk;
my $text = "this is a test...";
my $mw = new MainWindow;
$mw->Label(-textvariable=>\$text)->pack(-fill=>'both');
$mw->repeat(200,[sub{$text=~s/(.)(.*)/$2$1/}]);
MainLoop;
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Based on marto's advice above.

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

Main( @ARGV );
exit( 0 );

sub Main {    
    my $mw = tkinit;
    my $marq = marq( $mw , [ 'Anonymous Monk loves the color pink and 
+pancakes', ] );

    $mw->Button(
        -text    => 'stop',
        -command => sub { $marq->{_marq_timer}->cancel; }
    )->pack( qw/ -anchor nw / );
    
    $marq->configure(qw/ -background pink /);
    $marq->pack(qw/-anchor nw /);
    
    marq( $mw , [ @INC ] )->pack(qw/-anchor sw -expand both /);
    
    $mw->MainLoop;
}

sub marq {
    my( $mw, $messages ) = @_;
    my $width = 20;
    $messages = ' ' x $width . join(' --- ', @$messages );
    my $position = 0;
    my $showthis = "";
    my $label = $mw->Label( -width => $width, -textvariable => \$showt
+his);
    $label->{_marq_timer} = $mw->repeat(
        50,
        sub {
            if( $position > length $messages ){
                $position = 0;
            }
            my $format = '%-'.$width.'s';
            my $newmsg = sprintf $format, substr $messages, $position,
+ $width;
            $position++;
            $showthis = $newmsg;
            return;
        },
    );
    return $label;
};

__END__
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