my @seen;
foreach my $target (@integer_data_set) {
    if(defined($seen[$target]) {
        print "Duplicate: $target\n";
        next;
    }
    $seen[$target] = 1;
    print "New: $target\n";
}

##</code><code>##

my %seen;
foreach my $target (@string_data_set) {
    if (exists($seen{$target}) {
        print "Duplicate: $target\n";
        next;
    }
    $seen{$target} = 1;
    print "New: $target\n";
}

##</code><code>##

sub hash {
    my $string     = shift;
    my $buckets    = 100;
    my $hash_value = 0;

    foreach my $ordinal (map {ord} split(//, $string)) {
        $hash_value = ($hash_value + $ordinal) % $buckets;
    }
    return $hash_value;
}

##</code><code>##

sub find {
    my ($storage_aref, $needle) {
    my $hashed = hash($needle);
    if(defined($storage_aref[$hashed)) {
        my $found_ix = first_ix {$needle eq $storage_aref->[$hashed]->[$_]->[0]} @{$storage_aref->[$hashed]};
        return $storage_aref->[$hashed]->[$found_ix]->[1];
    }
    return;
}

##</code><code>##

$storage_aref = [
    [ # Bucket 0.
        ['string' => 'value'],
        ['another' => 'other value'],
    ],
    [ # bucket 1.
        ['something' => 'its value'],
    ],
    [...], # Bucket 2,
    ...
];