while (ptb.hasNext()) {
CoreLabel w = ptb.next();
Matcher m = sgml.matcher(w.word());
if (m.matches()) {
prepend.append(w.before()).append(w.word());
previous.appendAfter(w.word() + w.after());
} else {
if (prepend.length() > 0) {
w.prependBefore(prepend.toString());
prepend = new StringBuilder();
}