How to use tab stops in underlines sections in LaTeX?

How can I use tab stops and underline at the same time? I need to draw something like:

X Y Z
-----
  A B C
  -----
    P Q R
    -----

My first thought was tabbing and underline, but putting tab stops in an underline section seems to break the stops:

\begin{tabbing}
\underline{X \= Y Z} \\
\> \underline{A \= B C} \\
\> \> \underline{P \= Q R}
\end{tabbing}

Is there a way to escape the tab stops? Or just a better way altoget开发者_如何学Cher?

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Maybe an overkill but PSTricks offers almost unlimited drawing, formatting capabilities.