Note also that the height and width of a window are passed in unsigned shorts, so that the max width of a window is 65535 pixels. There are not that many displays that are 65535 pixels wide...

You could ->pack and ->packForget in a non-scrolled Pane using the scrollbar to control which of your large array of Labels are packed. Only pack a screen widths of subwidgets at a time.

Or only create a screen widths of Label widgets, then change their contents based on the scrollbar.

Or scroll in two dimensions.

#!/usr/bin/perl

use strict;
use warnings;
use Tk;
use Tk::Pane;

my $mw = MainWindow->new();
$mw->geometry('500x500');

my $pane = $mw->Scrolled( 'Pane', -scrollbars => 'se' )->pack( -side =
+> 'left', -fill => 'both', -expand => 1 );

my $perrow = 100;
foreach my $col ( 1 .. 1000 )
  {
  my $txt = "Col $col";  # doesn't work
  $pane->Label( -text => $txt, -relief => 'groove', -height => 20,
    )->grid( -row => int +($col - 1) / $perrow,
    -column => ($col - 1) % $perrow );
  }

MainLoop;
[download]

And here's an example of making a fixed number of Labels and changing the data in each with a scrollbar.

#!/usr/bin/perl

use strict;
use warnings;
use Tk;
use Tk::Pane;

my $offset = 0;
my $labelcount = 7;

my $mw = MainWindow->new();
$mw->geometry('500x500');

my $pane = $mw->Scrolled( 'Pane', -scrollbars => 'se' )->pack( -side =
+> 'left', -fill => 'both', -expand => 1 );

my @data = map "Col $_", 1 .. 1000;

$pane->Scale(-orient => 'horizontal', -from => 0,
  -to => @data - $labelcount, -variable => \$offset, -command => \&sho
+w,
  -showvalue => 0,
  )->pack(-fill => 'x', -side => 'bottom');
my @labels = map
  {
  $pane->Label( -text => $data[$_], -relief => 'groove',
    -height => 20, -width => 8,
    )->pack( -side => 'left' );
  } 0 .. $labelcount - 1;

MainLoop;

sub show
  {
  my $i = $offset;
  for ( @labels )
    {
    $_->configure( -text => $data[$i++] );
    }
  }
[download]