re = /[Aa][Tt][Uu][0-9]{8}\D/
str = 'ATU12345678
AT123456789
AT12345678
DE123456789
DE1234567a9
DE12345678
DE1234567899
'
# Print the match result
str.scan(re) do |match|
puts match.to_s
end
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html