> I then find that the module refers to a method
> "h". I know rails
> has a helper method "h", but cannot otherwise find one, despite all my
> grep -ir "def h"  on the entire standard library and all gems

That's because h is an alias for html_escape (defined in ERB::Util).
Do grep "alias h html_escape" on your standart library and you will
most likely find it.
Take a look at
actionpack/lib/action_view/template_handlers/erb.rb in rails and
/usr/lib/ruby/1.8/erb.rb in ruby standard lib (your paths may differ).

Regards,
Rimantas
--
http://rimantas.com/