I have a potentially super-fast mechanism. Hash slices: 
my %seen;
@seen{@larger_list} = ();
delete @seen{@smaller_list};

my @culprits = keys %culprit;

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However, if you have the data in files to begin with, it's probably best NOT to put them in arrays.

japhy -- Perl and Regex Hacker

In reply to Re: using hash uniqueness to find the odd man by japhy
in thread using hash uniqueness to find the odd man by novitiate

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