%% 
%%  Ein Beispiel der DANTE-Edition
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%%  2. Auflage
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%%  Beispiel 17-04-1 auf Seite 846.
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%%  Copyright (C) 2016 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
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\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{352.81416pt}
\setlength\parindent{0pt}
%StartShownPreambleCommands
\usepackage{l3regex}
%StopShownPreambleCommands
\begin{document}
\ExplSyntaxOn
\tl_set:Nn \l_my_tl { Das~ist~wunderbar. } \l_my_tl\par
\regex_replace_once:nnN { wunderbar } { schrecklich }\l_my_tl
\l_my_tl\par
\regex_replace_all:nnN { \w+ } { \0 , } \l_my_tl
\l_my_tl\par
\ExplSyntaxOff
\end{document}