\newcommand in preamble produces error

Both \def\foo{bar} and \newcommand\foo{bar} , used in

<verbatim>
  * Set LATEXMODE_PREAMBLE =
</verbatim>

on the page Main.SitePreferences result in the error

! LaTeX Error: Missing \begin{document}.

when %$\foo$% is used on a page. \renewcommand and \definecolor both work as expected. So, how can I introduce a new command?

-- ShaughanLavine - 15 Jan 2011