#!/usr/local/bin/perl -w
use strict;
use Tk;
use IO::File;

sub readfile
{
 my ($t,$fh) = @_;
 my $size = (stat($fh))[7];
 my $len  = $size - $t->{'posn'};
 if ($len > 0)
  {
   my $buffer = "";
   my $got = sysread($fh,$buffer,$len);
   $t->insert('end',$buffer);
   $t->{posn} += $got;
   $t->see('end');
  }
}

my $mw = MainWindow->new;

my $fh = IO::File->new("<$ARGV[0]");

my $t  = $mw->Scrolled('Text',-scrollbars => 'w');

$t->pack(-expand => 1, -fill => 'both');

$t->{posn} = 0;

$t->repeat(5000,sub { readfile($t,$fh) } );

MainLoop;