@setfilename foo.info
@setcontentsaftertitlepage
@settitle Foo
@titlepage
@title Foo
@end titlepage
@contents
As far as I can imagine (I didn't try it), in this example document,
@contents is already "after the title page", so you wouldn't see any
differences in the output whether @setcontentsafter... was used or not.
If you put some text (like, historically, the entire manual :) between
the @end titlepage and the @contents, you would. -k
