if ($window_start > 0) {
        $text_body =~ /\S+/g foreach 1..$window_start;
        $start_index = pos($text_body); 
}  else {
        $start_index = 0;
}

$text_body =~ /\S+/g foreach 1..$window_size; 

$end_index = pos($text_body); 

$windowed_text = substr($text_body, $start_index, ($end_index - $start_index));