[texhax] visibility of variables through \rput

[Karl Berry]

    And, not specifically for scoping but for other low-level things, the
    LaTeX source itself (the source2e.pdf file somewhere in your texmf tree)
    is much more helpful than your average source code, since it's written in
    literate programming style.

I echo that, and let me mention that for people who like to read on
paper, it's available at http://www.lulu.com/content/837928, thanks to
Tim Arnold.