FORMAT = /([0,1]{1})?([-| \.]+)?\(?([0-9]{1,3})\)?([- \.]+)??([0-9]{3})([- \.]?)+([0-9]{4})/

phone_numbers = [
  "(520) 999.9999", "520.999.9999", "(520) 999 9999", 
  "5209999999", "(520)-555-5555", "520.999.9999"]
phone_numbers.each do |pn|
  p pn.match(FORMAT)[0]
end