%% 
%%  Die DANTE-Edition
%%  Ein Beispiel der LaTeX Referenz
%%  3. Auflage
%% 
%% 
%%  Copyright (C) 2013 Herbert Voss
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 
%% 
%% ==== 
% Show page(s) 1
%% 
%% 
\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{121.16928pt}
\setlength\parindent{0pt}
%StartShownPreambleCommands
\usepackage{xparse}
\NewDocumentEnvironment{Section}{ om }
 { \IfNoValueTF{#1} { \section{#2} } { \section[#1]{#2} }
 }{}
\NewDocumentEnvironment{Section*}{ m }{\section*{#1}}{}
%StopShownPreambleCommands
\begin{document}
\tableofcontents
\begin{Section}{Foo}
foo
\end{Section}
\begin{Section}[BAR]{Bar}
bar
\end{Section}
\begin{Section*}{Baz}
baz
\end{Section*}
\end{document}