The problem is that in your for loop you are removing elements from the array, but your loop will continue iterating until $#display, the size of the array when your loop began. Then within the loop, you are accessing $display[$_][0], which will cause $display[$_] to spring into existence and contain an array reference as its value, even if there is currently no element at index $_. My suggestion is to just use the array reference directly instead of splicing it out and back in: 
my $row;
for my $temp (@display) {
    if ($temp->[0] =~ /^$number$/i) {
         $row = $temp;
    }
}
unless ($row) {
    $row = [$number,' ',' ',' ',' '];
    push @display, $row;
}
$row->[$j] = 'X';

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In reply to Re: Populate and sort AoA by Errto
in thread Populate and sort AoA by nedals

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