QRegExp Escaping special characters problems detecting word boundaries

When using \b escaped special characters fail to match

For Eample :

QString test = QString("foo $40");
test.replace(QRegExp("\\b\\$40
b"), "foo");
qDebug() << (test == "foo foo" ? "success" : "failure"); //failure

Escaping a special character e.g.
$ should make QRegExp see it as a normal character.

This happens for all special characters except _