Counting needs two steps: Setting the counter to 0 before the loop and the incrementing step:

#Initialize the counter before the loop
my $true_positives=0;

while(<INPUT2>){
...

          #instead of the push
          $true_positives++;

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That's it, $true_positives has the number of positive results after the loop

In reply to Re^4: Reading two files, cmp certain cols by jethro
in thread Reading two files, cmp certain cols by sesemin

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