-# reads global.sym, pp.sym, perlvars.h, intrpvar.h, thrdvar.h, config.h
-# On OS/2 reads miniperl.map and the previous version of perl5.def as well
+# Reads from information stored in
+#
+# config.h
+# config.sh
+# global.sym
+# globvar.sym
+# intrpvar.h
+# miniperl.map (on OS/2)
+# perl5.def (on OS/2; this is the old version of the file being made)
+# perlio.sym
+# perlvars.h
+#
+# plus long lists of function names hard-coded directly in this script and
+# in the DATA section.
+#
+# Writes the result to STDOUT.
+#
+# Normally this script is invoked from a makefile (e.g. win32/Makefile),
+# which redirects STDOUT to a suitable file, such as:
+#
+# perl5.def OS/2
+# perldll.def Windows
+# perl.exp AIX
+# perl.imp NetWare
+