That's easy with List::Compare::Functional:

#!/usr/bin/perl -sl

use strict;
use warnings;
use List::Compare::Functional qw(:main);

my @Llist = qw(aa bb ac ad);
my @Rlist = qw(bb cc cd);
my @Ronly = get_complement( [\@Llist, \@Rlist] );
print "@Ronly";
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