Net::HTTP and post_form

I expected this to work (since the #post_form method is documented), but
the method is not found:

require ‘net/http’

Net::HTTP.start(‘’, 4567) do |http|
http.post_form(’/foo’, “bar” => “baz”)

Here’s the error:

http-post-bug.rb:4: undefined method post_form' for #<Net::HTTP open=false> (NoMethodError) from /usr/local/lib/ruby/1.8/net/http.rb:543:instart’
from /usr/local/lib/ruby/1.8/net/http.rb:440:in `start’
from http-post-bug.rb:3

Why isn’t post_form usable in the block form? I’m using the block form
because it’s actually going thru a proxy.

I can do it myself by creating the request manually:

   req =
   req.form_data = params'', 4567).start {|http|

but it’s kind of disappointing.