private static HashMap clonePreexists(final HashMap old) {
		final HashMap clone = new HashMap();
		final Iterator vars = old.keySet().iterator();
		while (vars.hasNext()) {
			final LocalVariable var = (LocalVariable) vars.next();
			final HashSet set = (HashSet) old.get(var);
			if (set == null) {
				clone.put(var, null);
			} else {
				clone.put(var, set.clone());
			}
		}
		return (clone);
	}