# supposing the program output is all stored in $text:

$text =~ s/.*\r//g;


##</code><code>##

# you need to know which line number you're at in the Tk::Text buffer
# -- let's suppose that's in a variable called "$line_number"

  @updates = split( /\r/, $latest_output );
  for my $string ( @updates ) {
      $tktext_widget->SetCursor( "$line_number.0" ); # go to start of that line;
      $tktext_widget->deleteToEndofLine;
      $tktext_widget->Insert( $string );
      $line_number += ( $string =~ tr/\n// );
  }