a complicated way.
The command-line arguments to \cw{multi} include a command, a set of
-filenames, and a fragment of Perl. for each of the filenames,
+filenames, and a fragment of Perl. For each of the filenames,
\cw{multi} will use the fragment of Perl to transform the filename
into a new filename, and will then invoke the given command, passing
the old and new filenames as arguments.