my @ary1 = (1, 2, 3, 4, 5, 6, 7);
my @ary2 = (6, 7, 8, 9, 10, 11);

my %h1 = map {$_ => 1} @ary1;
my %h2 = map {$_ => 1} @ary2;

my %dupes;
@ary1 = grep {(! (exists $h1{$_} and exists $h2{$_})) or do{$dupes{$_}=1;0}} @ary1;
@ary2 = grep {(! (exists $h1{$_} and exists $h2{$_})) or do{$dupes{$_}=1;0}} @ary2;

print "ary1 is @ary1 \n";
print "ary2 is @ary2 \n";
my @dupes = keys %dupes;
print "dupes were @dupes \n";