The warning is there to help you. If you know you are going to be trying to treat null strings as numbers, turn it off: 

use strict;
use warnings;
use 5.010;

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


for my $index (0 .. 2) {
    no warnings 'numeric';
    say $arr1[$index] + $arr2[$index];
}
__END__
c:\test>junk
1
3
4

[download]

And you can prevent the used only once warning, by using them twice. Eg. add a line $a = $b;.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
"I'd rather go naked than blow up my ass"

In reply to Re: converting strings to ints by BrowserUk
in thread converting strings to ints by 7stud

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