This is the code from perlfaq4, and it also says
It assumes that each element is unique in a given array

Is that the case for your arrays? If not, it would explain the difference.

Update: See almut's reply below, this code is nonesense.

(Update:) I'd just store one array in the hash, something along these lines: (untested) 

my (@intersection, @union);
my %count;
@count{@array1} = undef;
for (@array2) {
    if (exists $count{$_}) {
          push @union, $_;
    } else {
          push @intersection, $_;
    }
}

[download]

(Second update): Any idea why the answer in the FAQs makes such an IMHO needless assumption? The code without that assumption isn't much longer, and although I haven't benchmarked it I don't think it's much slower either (I even think it uses less memory).

In reply to Re: Difference of array by moritz
in thread Difference of array by sandy1028

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