%%
%% The LaTeX Companion, 3ed
%%
%% Example 3-2-9 on page I-153 in "xspace --- Gentle spacing after a macro".
%%
%% 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{xspace}
  \newcommand\marker{\textsuperscript{*}\xspace}
  \newcommand\GB {Great Britain\xspace}
  \newcommand\EU {European Union\xspace}
%StopShownPreambleCommands

\begin{document}
  In 2017 \GB\marker voted for leaving the \EU\marker.
  \par \xspaceaddexceptions{\marker}
  In 2017 \GB\marker voted for leaving the \EU\marker.
\end{document}