That's easy enough. Using List::Compare:

#!/usr/bin/perl

use strict;
use warnings;
use List::Compare;

my @arr1 = (1, 2, 3, 4, 5, 6, 7, 8, 9);
my @arr2 = (1, 4, 5, 9 ,7);

my $lc = List::Compare->new(\@arr1, \@arr2);
my @arr3 = $lc->get_unique;
print "@arr3\n";
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