field = child(modiferTree, 0).getText();
modifier.pop(field);
break;
case MqlParser.SHIFT:
field = child(modiferTree, 0).getText();
modifier.pop(field);
break;
case MqlParser.PULL:
field = child(modiferTree, 0).getText();
value = readVariableLiteral(child(modiferTree, 1), ctx);
modifier.pull(field, value);