Thank you so much, everybody :)

My apologies for not making some things clearer in my haste to simplify the question.

In my code above, the array @weights is pre-defined so I should not have that line to assign each token "0" because it can't possibly be undefined - this enlightenment came after reading the wonderful feedback that I've got from your replies.

The other array @digits is the result of an input from a web form. Specifically, it's an identification number of the shape 9525423E. @digits is gotten using a split: 

# $input is received from a web submission,
# assigned a value here for simplification
$input = '9525423E';
@digits = split //, $input;
my $letter = uc(pop @digits);

[download]
So @digits should contain 7 numeric characters after the pop. But users may enter an invalid identification number, e.g one that contains only 6 digits instead of 7. So the extra code is need to assign each individual element of @digits a value to prevent the "Use of uninitialized value..." warning.

Cheers!

In reply to Re: A better way than || by Anonymous Monk
in thread A better way than || by Anonymous Monk

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