\documentclass{ltxdoc}
\input{xepersian-doc-preamble.ltx}
\begin{document}
\section{New Conditionals}
\subsection{Shell escape (or write18) conditional}
\begin{BDef}
\Lcs{ifwritexviii}\\
\qquad\textcolor{myred}{\Larga{material when Shell escape (or write18) is enabled}}\\
\Lcs{else}\\
\qquad\textcolor{myred}{\Larga{material when Shell escape (or write18) is not enabled}}\\
\Lcs{fi}
\end{BDef}
\end{document}