gistfile1.rb

case
when options.key?("car")
  # Validate car
when options.key?("driver")
  # Validate driver
else
  # If no other statement matches, error out
end

gistfile2.rb

if options.key?("car") || options.key?("driver")
  validate_car(options["car"]) if options.key?("car")
  validate_driver(options["driver"]) if options.key?("driver")
else
  raise StandardError, "..."
end