ruby.rb

# Pastebin JZkBjUFr
    uri = URI.parse("https://secure.com/")
    pem = File.read("/path/to/my.pem")
    http = Net::HTTP.new(uri.host, uri.port)
    http.use_ssl = true
    http.cert = OpenSSL::X509::Certificate.new(pem)
    http.key = OpenSSL::PKey::RSA.new(pem)
    http.verify_mode = OpenSSL::SSL::VERIFY_NONE

    request = Net::HTTP::Get.new(uri.request_uri)

I got it:

#!/opt/puppetlabs/puppet/bin/ruby

require 'net/http'
require 'openssl'
require 'json'

cert    = File.read('/etc/puppetlabs/puppet/ssl/certs/puppet.athome.priv.pem')
privkey = File.read('/etc/puppetlabs/puppet/ssl/private_keys/puppet.athome.priv.pem')
ca_file = '/etc/puppetlabs/puppet/ssl/certs/ca.pem'

query  = 'resources[parameters, certname]{ title = "Puppetserver::Params" and type = "Class" }'
params = { :query => query }

uri       = URI('https://puppet.athome.priv:8081/pdb/query/v4')
uri.query = URI.encode_www_form(params)

Net::HTTP.start(
  uri.host, uri.port,
  :use_ssl     => uri.scheme == 'https',
  :cert        => OpenSSL::X509::Certificate.new(cert),
  :key         => OpenSSL::PKey.read(privkey),
  :ca_file     => ca_file,
  :verify_mode => OpenSSL::SSL::VERIFY_PEER,
) do |http|

  request  = Net::HTTP::Get.new(uri)
  response = http.request request

  p JSON.parse(response.body)

end