Add fileinput.
diff --git a/Doc/lib/libundoc.tex b/Doc/lib/libundoc.tex
index 56a71a4..76062c2 100644
--- a/Doc/lib/libundoc.tex
+++ b/Doc/lib/libundoc.tex
@@ -32,6 +32,8 @@
 
 multifile.py -- make each part of a multipart message ``feel'' like
 
+fileinput.py -- convenient loop over the lines in a list of input files.
+
 
 \section{Miscellaneous useful utilities}