if (_token.type == TokenType.String) {
eval = new LiteralExpr(_token.text);
next(false);
} else if (_token.type == TokenType.Regex) {
RegexToken t = (RegexToken) _token;
try {
Pattern pattern = Pattern.compile(_token.text, t.caseInsensitive ? Pattern.CASE_INSENSITIVE : 0);
eval = new LiteralExpr(pattern);
next(false);