my @new_list = map { $_->[0] }
                 sort { $a->[1] cmp $b->[1] }
                   map { /(a|b)(\d+)_(\d+)\[(\d+)\]/ or die "Can't parse $_";
                         [$_, sprintf "$1%05d%05d%05d", $2, $3, $4]; 
                       } @split_list;