m4_include([subdirmk/subdirmk.ac])
SUBDIRMK_SUBDIRS([...list of subdirectories in relative syntax...])
-Write a Dir.sd.mk in each directory. The toplevel one should
-probably contain:
+Write a Dir.sd.mk in each directory. See the substitution syntax
+reference, above, and the example/ directory here. The toplevel
+Dir.sd.mk should probably contain:
include subdirmk/usual.mk
include subdirmk/regen.mk