The contents of filename
will be inserted wherever the
If the file is specified with an
will be interpreted as RD documentation.
If the filename has no extension,
will look for a file with an
extension that matches the type of output being produced (
for HTML files,
for man files, and so on) and interpolate
that file's contents in the
stream. Thus, a line such as:
could be used to add an output-dependent header to a document.