This is addressed in perlfaq4 at How do I compute the difference of two arrays. The code there could be adapted to your specific need pretty easily.

Here's the code from perlfaq4:

 my (@union, @intersection, @difference);
    my %count = ();
    foreach my $element (@array1, @array2) { $count{$element}++ }
    foreach my $element (keys %count) {
        push @union, $element;
        push @{ $count{$element} > 1 ? \@intersection : \@difference }
+, $element;
    }
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Here's one way to adapt it.

sub difference {
    my $array_ref1 = shift;
    my $array_ref2 = shift;
    my @difference;

    foreach my $element (@$array_ref1, @$array_ref2) { $count{$element
+}++ };
    foreach my $element (keys %count) {
        push @difference, $element if $count{$element} == 1;
    }
    return \@difference;
}
[download]

(please do test it -- this is untested code.)

List::Compare and Set::Scalar will do this.

The method you want is get_symmetric_difference for List::Compare or symmetric_difference for Set::Scalar.

And the faq that KurtZ referenced.

C:\Old_Data\perlp>perldoc -q "intersection"
Found in C:\Perl64\lib\pods\perlfaq4.pod
  How do I compute the difference of two arrays?  How do I compute the
+ intersection of two arrays?
    Use a hash. Here's code to do both and more. It assumes that each
    element is unique in a given array:

            @union = @intersection = @difference = ();
            %count = ();
            foreach $element (@array1, @array2) { $count{$element}++ }
            foreach $element (keys %count) {
                    push @union, $element;
                    push @{ $count{$element} > 1 ? \@intersection : \@
+difference }, $element;
                    }

    Note that this is the *symmetric difference*, that is, all element
+s in
    either A or in B but not in both. Think of it as an xor operation.


C:\Old_Data\perlp>
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> Use hash slices to create hashes and delete via hash slice.

like this Using hashes for set operations... ? :)

update

use strict;
use warnings;
use Data::Dump qw/pp dd/;


my @Llist = qw(abel abel baker camera delta edward fargo golfer);
my @Rlist = qw(baker camera delta delta edward fargo golfer hilton);

my %tmp;

@tmp{@Rlist} = @Rlist;

delete @tmp{@Llist};

pp values %tmp;
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"hilton"

please note this is restricted to keys with different string representation.

Cheers Rolf
_{(addicted to the Perl Programming Language and ☆☆☆☆ :)
Wikisyntax for the Monastery}