I have sample code that works. I can select the whole string or any part of it and paste it somewhere else.

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

use Tk;
use Tk::ROText;

my $mw = 'MainWindow'->new;

my $t = $mw->ROText->pack;
$t->Contents('Just another Tk hacker,');

MainLoop();
[download]

Can you show the code that doesn't work?