I'm not sure what your problem really is, but from what I can guess, you should split your data before you load it into the text box. The sample data you show, displays Ok, and you could use an approach similar to huge pad to display it.

Before even trying to display the data, I would split it, and load it into a hash. Then work out a scheme, for the text widget just to display a designated number of hash elements, like huge pad. Then when you want to save the whole file, just loop thru all the hash keys and save(concantate) the values.

And don't overlook the power that tags can add to your program, here is a simple example.

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

my $mw = tkinit;
my $t = $mw->Scrolled('Text',
              -scrollbars => 'osoe'
               )->pack;

for(1..100){
  $t->tagConfigure( 'data'.$_, -data => $_ x 20,
);
}

for(1..100){
 $t->insert('end', 'Line'."$_\n", ['datarider','data'.$_ ]);
}

$t->tagBind( 'datarider', '<Enter>', sub { getdata($t) } );
$t->tagBind( 'datarider', '<Leave>', sub { getdata($t) } );
$t->bind( '<Motion>', sub{ getdata($t) } );


MainLoop;

sub getdata {
    my ( $text_widget ) = @_;

    my $x = $text_widget->pointerx - $text_widget->rootx;
    my $y = $text_widget->pointery - $text_widget->rooty;
    #print "$x $y\n"; 
    my $txt_index = $text_widget->index( '@' . $x . ',' . $y );
    #warn $txt_index; 
    my ( $line, $char ) = ( $txt_index =~ /^(.+?)\.(.+?)$/ );
    my @tags =  $text_widget->tagNames($txt_index);
    print "@tags\n";

    foreach my $tag(@tags){
       print $text_widget->tagCget($tag,'data'),"\n";
      }

}
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