Match one of three number plate patterns

anpr.rb

formats = [
  "[A-Z]{2}[0-9]{2}[A-Z]{3}",
  "[A-Z]{1}[0-9]{3}[A-Z]{3}",
  "[A-Z]{3}[0-9]{3}[A-Z]{1}"
]

pattern = /\A#{formats.join("|")}\z/

candidates = %w[
  RF10AK0
  RF1OAK0
  RF1OAKO
  RF10AKO
]

match = candidates.detect(-> { "No Match" }) do |candidate|
  candidate.match?(pattern)
end

puts "Result: #{match}"

output.txt

$ ruby anpr.rb
Result: RF10AKO