":aa2bb4cc6dd8" =~ / (:)
                     (?{ [[], []] })   # initialize $^R
                     (?:
                         (\w\w) (\d)
                         
                         # add captures to $^R:
                         (?{ [[@{$^R->[0]}, $2], [@{$^R->[1]}, $3]] })
                     )*
                   /x;

dd $&;       #->  ":aa2bb4cc6dd8"
dd $1;       #->  ":"
dd $^R->[0]; #->  ["aa", "bb", "cc", "dd"]
dd $^R->[1]; #->  [2, 4, 6, 8] }