TeXでverbatimとeclbkboxの組み合わせ。
http://oku.edu.mie-u.ac.jp/~okumura/texfaq/qa/24810.html
上記より引用。以下の記述を組み込めばうまくいきました。
\makeatletter \def\breakbox{% \vskip\breakboxskip\relax \setbox\bk@bxb\vbox\bgroup \advance\linewidth -2\fboxrule \advance\linewidth -2\fboxsep \hsize\linewidth\@parboxrestore \@setminipage%%% added \parindent\breakboxparindent\relax} \def\endbreakbox{% \ifvmode \vskip-\lastskip \fi%%% added \egroup \ifhmode\par\fi {\noindent\bk@lcnt\@ne \@bkconttrue\baselineskip\z@\lineskiplimit\z@ \lineskip\z@\vfuzz\maxdimen \bk@split\bk@addfsepht\bk@addskipdp \ifvoid\bk@bxb % Only one line \def\bk@fstln{% \bk@addfsepdp \vbox{\hrule\@height\fboxrule\bk@line\hrule\@height\fboxrule}}% \else % More than one line \def\bk@fstln{\vbox{\hrule\@height\fboxrule\bk@line}\hfil \advance\bk@lcnt\@ne \loop \bk@split\bk@addskipdp\leavevmode \ifvoid\bk@bxb % The last line \@bkcontfalse\bk@addfsepdp \vtop{\bk@line\hrule\@height\fboxrule}% \else % 2,...,(n-1) \bk@line \fi \hfil\advance\bk@lcnt\@ne \if@bkcont\repeat}% \fi \leavevmode\bk@fstln \par}% \vskip\breakboxskip\relax} \def\verbatim@readfile#1{% \verbatim@startline \openin\verbatim@in@stream #1\relax \ifeof\verbatim@in@stream \typeout{No file #1.}% \else \let\@verbatim@prevline\relax%%% added \@addtofilelist{#1}% \ProvidesFile{#1}[(verbatim)]% \expandafter\endlinechar\expandafter\m@ne \expandafter\verbatim@read@file \expandafter\endlinechar\the\endlinechar\relax \closein\verbatim@in@stream \fi \verbatim@finish} \def\verbatim@read@file{% \read\verbatim@in@stream to\next \ifeof\verbatim@in@stream\else \ifx\@verbatim@prevline\relax\else \expandafter\verbatim@addtoline\expandafter{\@verbatim@prevline}% \verbatim@processline \verbatim@startline \fi \let\@verbatim@prevline\next \expandafter\verbatim@read@file \fi} \makeatother