\def\@progcr@ii#1{\csname @progcr@#1\endcsname\ignorespaces}
\@namedef{@progcr@+}{\prog@@cr[\medskipamount]}
\@namedef{@progcr@-}{\prog@@cr*[\jot]}
+\def\macsl{\`\textbackslash\hskip\leftmargin}
%% Put a chunk of text in a box.
\newenvironment{boxy}[1][\q@]{%