Not really. Even if the code uses both arrays then there is nothing preventing building a temporary hash through 
my %hash = map { $_ => 1 } @first_list;

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..and then discarding the hash after the check for new machines. More likely is that he is only interested in the second list, or just new machines, and they could be in an array just like before.
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In reply to Re^2: Use hashes instead of grep by space_monk
in thread How to grep exact string by Divakar

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