How to make nested underbraces (or overbraces) appear in a custom order?

Question

I need to nest a couple of underbraces. It works perfectly fine if nested inside-out:

\[
  \underbrace{2 + \underbrace{2 * 2}}
\]

yields:

However, I would rather like to have it outside-in, something like this: (pardon my art)

How can I order those braces this way?

Answer 1

With array:

\documentclass{article}

\begin{document}

\[
\renewcommand{\arraystretch}{0}
\begin{array}{@{}r@{}}
\underbrace{2+2\cdot2} \\
\underbrace{\hphantom{2\cdot2}}
\end{array}
\]

\end{document}

Sorry, but I can't stand multiplication denoted with an asterisk.