That's pretty trivial with map:

#!/usr/bin/env perl 
use strict;
use warnings;
use Data::Dumper;

my @rows = (
          [
            'AA1',
            'BB1'
          ],
          [
            undef,
            undef
          ],
          [
            111,
            101
          ],
          [
            222,
            202
          ],
          [
            333,
            303
          ],
          [
            444,
            404
          ],
          [
            555,
            505
          ],
          [
            666,
            606
          ],
          [
            777,
            707
          ],
          [
            888,
            808
          ],
          [
            999,
            909
          ]
);

my @bb1 = map { $_->[1] } @rows;
print Dumper \@bb1;
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