You should notice that Perl arrays are autovivified, where if you use an index out of range, the array will be auto-expanded.

So what you need is: use an array to record the sum of columns. each time you read a line, and add the columns to the sum array.

my @sum;

while (<FH>)
{
  chomp;
  my @F = split /\t/;
  $sum[$_] += $F[$_] for 0..@F-1;
}
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