G'day BrowserUk,

Using your 5 subarrays, I selected the middle one ([ 0, 10, 11, 19 ]): that should find the first and last subarrays as being the only ones not containing any of the integers: 0, 10, 11, 19.

I don't believe this should consume huge amounts of memory:

#!/usr/bin/env perl -l

use strict;
use warnings;

my @AoA = (
    [ 2, 13, 3, 16 ],
    [ 10, 1, 11, 6 ],
    [ 0, 10, 11, 19 ],
    [ 6, 1, 19, 15 ],
    [ 17, 6, 18, 12 ],
);

my $selected = $AoA[2];
my %unique = map { $_ => 1 } @$selected;

print "@$_" for grep { ! map { $_ ? $_ : () } @unique{@$_} } @AoA;
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Output:

2 13 3 16
17 6 18 12
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