sub aveAoA {
    my( $ref, $n ) = @_;
    my @sums;
    my $code = qq[ for my \$i ( 0 .. \$#\$ref ) { ];
    $code .= qq[ \$sums[ $_ ] += \$ref->[ \$i ][ $_ ];] for 0 .. $n -1;
    $code .= '}';

    eval $code;

    $sums[ $_ ] /= @{ $ref } for 0 .. $n -1;
    return @sums;
}

our $M ||= 1e6;
our $N ||= 4;

my @data; 
$#data = $M -1;
$data[ $_ ] = [ map int(-10+rand 20), 1.. $N ] for 0 .. $#data;

my @sums = aveAoA( \@data, $N );