Please explain what you mean by 'false positive'?

#!/usr/bin/perl
use strict;
use warnings;

sub are_both_zero
{
        my @array=@_;
        print "In the array (",join(', ',@array),"), ";
        if (!($array[0]+$array[1])) {
                print "both elements are zero.\n";
        } else {
                print "at least one element is not zero.\n";
        }
}

are_both_zero(3,-5);
are_both_zero(3,0);
are_both_zero(0,-5);
are_both_zero(0,0);
are_both_zero(3,-3);
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Output:

In the array (3, -5), at least one element is not zero.
In the array (3, 0), at least one element is not zero.
In the array (0, -5), at least one element is not zero.
In the array (0, 0), both elements are zero.
In the array (3, -3), both elements are zero.
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See also https://en.wikipedia.org/wiki/False_positive.

Alexander