In the case where the rows didn't all have the same number of columns:

my $col = 0;

while ( my @col_values = map { $_->[$col] } @AoA ) {
   last unless grep /^.$/, @col_values;
   print join (",", @col_values), "\n";
   $col++;
}
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Although I'm sure there is a more elegant way to write it.