An illustration to see whether I understand your problem: I create an array of array refs with 5 lines (instead of your 15 to keep it small) and 11 columns (0 to 10) called @lookback. Then I extract column number 3 (the fourth column) from this AoA, result called @column. Is that the right direction?

use strict;
use warnings;
use Data::Dumper;

my @lookback;
for my $line (1..5) {
    push @lookback, [ map { "$line.$_" } 0..10 ]; 
}

print Dumper \@lookback;

my $col = 3;
my @column = map { $_->[$col] } @lookback;

print Dumper \@column;
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