If I understand you correctly, you're seeing some kind of progress indicator or meter; something which looks fine in the terminal window (because each line overwrites previous lines), but of course it looks bad in the Tk::Text window, just as it would if the terminal window displayed each line of text on a separate physical line.

A couple of suggestions come to mind.  First off, if you don't need the \r separated lines, just throw them away.  If the status they're giving you is helpful, you could always parse them, and use the indication to update some actual status meter (such as you'd get with Tk::StatusBar or Tk::ProgressBar).

Another option would be to use tags in the Text window, and each time you receive output which would have overwritten the previous line, have the Text widget erase the previous line and replace it with the new one, to achieve the same effect.

Of these two, my choice would be to go with the first; it's more in the spirit of GUIs in general, and Perl/Tk specifically.

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

$text =~ s/.*\r//g;
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update: And as for actually making Tk::Text emulate a normal terminal display, you would need to keep track of the current line number in the text buffer (where the next chunk of program output will go), something like this:

# 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// );
  }
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