Group doc_type(?<doc_type>[A-Z]{1}) {1}matches one character from the set below:
A-Zone character from A (6510) to Z (9010) (case sensitive)
\/the literal / (4710 / 578 / 2F16)
Group country(?<country>[A-Z]{2}) {2}matches exactly 2 characters from the set below:
A-Zone character from A (6510) to Z (9010) (case sensitive)
\/the literal / (4710 / 578 / 2F16)
Group series_number(?<series_number>\w*) \w*any word character, repeated any number of times
\/the literal / (4710 / 578 / 2F16)
.*any character (except for line terminators), repeated any number of times
g modifier: global. Finds all matches instead of stopping after the first
m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string