There is probably a way to keep track of the line length from the text widget's methods, but here is a brute approach.

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

my $mw=tkinit;
my $textarea = $mw->Scrolled("Text",
                             -scrollbars => 'ose',
                             -width =>80,
                             -wrap =>'word',

                             )->pack;

$mw->after(1000,\&filltext);
MainLoop;

sub filltext
{
  my $length = 0;
  for (1..200){

    if($length > 30){$textarea->insert('end', "\n");; $length = 0}
    $textarea->insert('end', "$_ ");
    $length += length("$_ ");
    $textarea->see('end');
    $textarea->idletasks;
    $mw->after(10);

  }
}
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