docs: public Value get(Environment in) {
          while (true) {
              if (log.isDebugEnabled())
                  log.debug("looking up in " + in + '(' + in.expandedStringForm() + ')');
  			final Value retValue = values.get(in.expandedStringForm());
              if (retValue != null)
                  return retValue;
              if (!in.isReduceable())
                  return null;
              in = in.reduce();
          }
      }