class WWW::Mechanize

def post(url, query={})

agent.post('http://example.com/', [ ["foo", "bar"] ])
or
agent.post('http://example.com/', "foo" => "bar")
Example:
parameters can be passed as a hash, or as an array of arrays.
Posts to the given URL wht the query parameters passed in. Query 
def post(url, query={})
  node = {}
  # Create a fake form
  class << node
    def search(*args); []; end
  end
  node['method'] = 'POST'
  node['enctype'] = 'application/x-www-form-urlencoded'
  form = Form.new(node)
  query.each { |k,v|
    if v.is_a?(IO)
      form.enctype = 'multipart/form-data'
      ul = Form::FileUpload.new(k.to_s,::File.basename(v.path))
      ul.file_data = v.read
      form.file_uploads << ul
    else
      form.fields << Form::Field.new(k.to_s,v)
    end
  }
  post_form(url, form)
end