[texhax] Curious bug in breakcites

[Michael Barr]

If you compile the file:

\documentclass{article}
\usepackage{breakcites}
\newcommand{\etal}{\emph{et al.}}
\begin{document}
\cite{ABC}
\begin{thebibliography}{99}
\bibitem[A \etal\ (2000)]{ABC}
\end{thebibliography}
\end{document}

the output has an extra comma after the citation.  So far, I have found 
two ways to fix it:  take the period out of the definition of \etal and 
add it to the bibitem itself; or alter the definition of \@citex by 
replacing the last line of \@citex
        {\csname b@\@citeb\endcsname}}}{#1}}
with
        {{\csname b@\@citeb\endcsname}}}}{#1}}
(i.e. add another level of grouping).  Incidentally, the original last 
line was
        {\hbox{\csname b@\@citeb\endcsname}}}}{#1}}
and that \hbox was what prevented the citations from breaking.  I do not 
understand why that extra level of grouping has that effect, or for that 
matter why the period in the definition of \etal has that effect, but it 
is clearly a bug.

-- 
Any society that would give up a little liberty to gain a little
security will deserve neither and lose both.

            Benjamin Franklin