How to specify "http request header" in OpenURI
According to the documentation, you can pass a hash of http headers as the second argument to open:
open("http://www.ruby-lang.org/en/", "User-Agent" => "Ruby/#{RUBY_VERSION}", "From" => "foo@bar.invalid", "Referer" => "http://www.ruby-lang.org/") {|f| # ... }