**Use case**
`SELECT POSITION('/' IN s) FROM (SELECT 'Hello/World' AS s);`

The same as `position(s, '/')`

return false;
    ++pos;
    ASTPtr column_list;
    ASTPtr regex_node;
    if (!columns_p.parse(pos, column_list, expected) && !regex.parse(pos, regex_node, expected))
        return false;
    if (pos->type != TokenType::ClosingRoundBracket)
        return false;
    ++pos;
    auto res = std::make_shared<ASTColumnsMatcher>();
    if (column_list)
    {
        res->column_list = column_list;
        res->children.push_back(res->column_list);
    }
    else
    {
        res->setPattern(regex_node->as<ASTLiteral &>().value.get<String>());
        res->children.push_back(regex_node);
    }
    ParserColumnsTransformers transformers_p(allowed_transformers);
    ASTPtr transformer;
    while (transformers_p.parse(pos, transformer, expected))
    {
        res->children.push_back(transformer);
    }
    node = std::move(res);
    return true;
}
bool ParserColumnsTransformers::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)