How do I remove this warning?

  foreach my $j ($col_start .. $#column) {

    $n[$j] += 0; # add this to remove warning msg

    $x[$n[$j]][$j] = $column[$j];
    $x_tot[$j] += $x[$n[$j]][$j];
    $n[$j]++;
  }
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Any other suggestions on my perl usage are also welcome

The lines:

my @n=0;
my @x_tot=0;
  my @g_jack_av=0;
  my @g_jack_err=0;
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Should be:

my @n;
my @x_tot;
  my @g_jack_av;
  my @g_jack_err;
[download]

As you don't have to assign a value to the first array element.