FWIW, here's another variation. It has the advantage of producing empty strings rather than undefined values for absent pattern elements, so no need for a conversion step. It also has the advantage, if such it be, of not using named captures with the possible overhead of tied-hashery. It passes all tests above.

$string =~ m{
    \A
    ([[:alnum:]]+?) (?= (?: \d+ [[:upper:]]{0,2})? \z)
    (\d*) ([[:upper:]]?) ([[:upper:]]?)
    \z     
    }xms;
[download]