use strict;
use warnings;
use 5.010;

my @arr1 = ("1", "", "");
my @arr2 = ("", "3", "4");


for my $index (0 .. 2) {
    say $arr1[$index] + $arr2[$index];
}

--output:--
Argument "" isn't numeric in addition (+) at 2perl.pl line 10.
1
Argument "" isn't numeric in addition (+) at 2perl.pl line 10.
3
Argument "" isn't numeric in addition (+) at 2perl.pl line 10.
4