I do not understand the question. I just populated the @f array as in the OP. I just used 
while (<DATA>) {
    my @f = (undef, split /,/);

[download]

as the @f in the OP is not zero based, but one based. There is no need to cast between strings and numbers in Perl.

لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

In reply to Re^3: Argument "" Isn't numeric in numeric eq (==) by choroba
in thread Argument "" Isn't numeric in numeric eq (==) by ler224

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