Copy List from the other account (requires twitter gem, and the twitter lists having the same name. )

copyList.rb

require 'twitter'

puts "Open browser and run below script in Console."
puts "$('.app-settings, .access').find('span:not(.heading):lt(2)').map(function(){ return $(this).text() }).toArray().join(':')"
print "Source: "
source_token = gets.chomp.split(':')
print "Target: "
target_token = gets.chomp.split(':')
print "Name: "
name = gets.chomp

client_from = Twitter::REST::Client.new do |config|
    config.consumer_key        = source_token[0]
    config.consumer_secret     = source_token[1]
    config.access_token        = source_token[2]
    config.access_token_secret = source_token[3]
end

client_to = Twitter::REST::Client.new do |config|
    config.consumer_key        = target_token[0]
    config.consumer_secret     = target_token[1]
    config.access_token        = target_token[2]
    config.access_token_secret = target_token[3]
end

list = client_from.list_members(name).to_a.map{|s| s.id }
list_sliced = list.each_slice(100).to_a

list_sliced.each do |members|
    client_to.add_list_members(name, members)
end