Well, in this particular set of data, $x maxes out at 500 and $y maxes out at 10,000. So yes, it's an indexing issue related to @{$aob[ $y - 1 ]} but nothing I've read points to a simple one-line solution that actually produces the proper output.

As is my usual, my current solution is a little sideways. In the section above calling popnum3:

foreach my $r (0 .. $total){
   $row[$r] = $aob[$r][$y - 1];
}
my @rowin   = grep { $_ ne q{} } @row;
$mean    = mean(@rowin);
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sub popnum3 {
    my ( $x, $y, $z, $mean ) = @_;
    $aob[$x][$y] = $mean * ( 1 + $z );
    return $aob[$x][$y];
}
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Supposedly @row = @{$aob[ $y - 1 ]} should be equivalent to

foreach my $r (0 .. $total){
   $row[$r] = $aob[$r][$y - 1];
}
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BTW, the grep is in there since I know that although the current parameters shouldn't produce any blanks in the output, other parameters will.

So you are trying essentially to strip out the $y - 1 column, assuming your AoA is $aob[row][column]? In that case, your code might look like:

my @row = map $_->[$y - 1], @aob;

If not, I'm really lost as to the spec.

YES! - well, it's actually mapping out as $aob[column][row] But that's a minor issue that's all though the whole project. Maybe my conventions are a little off from everyone else's. Wouldn't be the first time.

Be that as it may my @row = map $_->[$y - 1], @aob; gives me proper results in the output without resorting to a foreach loop.

Thank You