%%
%% The LaTeX Companion, 3ed
%%
%% Example 2-1-2 on page I-31 in "tagging --- Providing variants in the document source".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3exa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{135.0pt}
%StartShownPreambleCommands
\usepackage[doc]{tagging}
%StopShownPreambleCommands

\begin{document}
\tagged{doc}   {Typeset this if tag doc is used.}
\untagged{code}{Typeset this if tag code is not used.}
\iftagged{be}  {To be or}{Not to be!}  Which is it?   \par
\tagged{doc,code}{Typeset this for either doc or code.}
Typeset this \untagged{}{always}\tagged{}{never}!     \par
\usetag{code} \droptag{doc}
Now neither of the variants are typeset!
\tagged{doc}   {Typeset this if tag doc is used.}
\untagged{code}{Typeset this if tag code is not used.}
\end{document}