%% The LaTeX Companion, 3ed

%%
%% The LaTeX Companion, 3ed
%%
%% Example 3-4-38 on page I-199 in "url --- Typesetting \acsp {url}, path names, and the like".
%%
%% 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{159.0pt}

%StartShownPreambleCommands
\usepackage{url}
%StopShownPreambleCommands

\begin{document}
\url{^frank} and \mbox{\url{^frank}} (OK) \par
\url{^^frank} but \mbox{\url{^^frank}} (bad) \par
\end{document}