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Kinda depends what mean by "blank"?

If the file contains two successive tabs with nothing in between, the result of split will undef, and you can use defined-or:

my @a = map $_//'NA', split /\t/, $line;
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If there might be spaces, or empty quotes between the tabs, you need to use else.

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

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.

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