In article <AD4480A509455343AEFACCC231BA850F17C358 / ukexchange>,
  Elliott Hughes <ehughes / bluearc.com> writes:

> I know static checking isn't really Ruby's thing, but avoiding weirdness
> like parameters that are hashtables full of uncheckable parameters has to be
> a good thing! 

If the benefit of that is parameter checking, how about this style:

open("http://...", OpenURI::OptProgressProc => lambda {|s| ... })

OpenURI::OptProgressProc is a some constant of a symbol.
-- 
Tanaka Akira