Regex to get the Facebook Page ID from a given URL

gistfile1.rb

# Matches patterns such as:
#    https://www.facebook.com/my_page_id => my_page_id
#    http://www.facebook.com/my_page_id => my_page_id
#    http://www.facebook.com/#!/my_page_id => my_page_id
#    http://www.facebook.com/pages/Paris-France/Vanity-Url/123456?v=app_555 => 123456
#    http://www.facebook.com/pages/Vanity-Url/45678 => 45678
#    http://www.facebook.com/#!/page_with_1_number => page_with_1_number
#    http://www.facebook.com/bounce_page#!/pages/Vanity-Url/45678 => 45678
#    http://www.facebook.com/bounce_page#!/my_page_id?v=app_166292090072334 => my_page_id
#    http://www.facebook.com/my.page.is.great => my.page.is.great

/(?:https?:\/\/)?(?:www\.)?facebook\.com\/(?:(?:\w)*#!\/)?(?:pages\/)?(?:[\w\-]*\/)*([\w\-\.]*)/