sleep can't be infinite
The following snippet from the sleep(1) man page is incorrect:
point number may be specified in all formats required by
C99/XPG6, including constants such as "Inf" or "infinite".
The form "infinite" isn't accepted, however "infinity" is.
While looking at sleep(1), a couple of other issues are apparent:
having a separate ksh93 section is wrong as the command and
the builtin are really the same, and the reference to wait(3ucb)
should be removed.