} else if (_token.type == TokenType.Identifier) {
String text = _token.text;
next(false);
if (_token == null || _token.type != TokenType.Delimiter || !_token.text.equals("(")) {
eval = "null".equals(text) ? new LiteralExpr(null) : new VariableExpr(text);
} else if( "PI".equals(text) ) {
eval = new LiteralExpr(Math.PI);
next(false);
} else {
Function f = ControlFunctionRegistry.getFunction(text);