The module suggested by AppleFritter is certainly the easiest way.

But in case you want to do it yourself in pure Perl without using a module, the most idiomatic way to do it is probably to use a hash (or two hashes in this case). This command-line script (re-using AppleFritter sample data) should give you a gist on how to do it:

$ perl -E '
my %hash1 = ("abc" => [1, 2, 3, 4]);
my %hash2 = ("abc" => [1, 3, 5, 7]);
my %val1 = map {$_, 1} @{$hash1{abc}};
my %val2 = map {$_, 1} @{$hash2{abc}};
say "Values missing in hash2: ", join " ", grep {not exists $val2{$_}}
+ keys %val1;
say "Values missing in hash1: ", join " ", grep {not exists $val1{$_}}
+ keys %val2;
'
Values missing in hash2: 4 2
Values missing in hash1: 7 5
[download]

Please ask if there is something you don't understand.

Edit: I had not seen j0se's solution when I suggested mine. Although the two solutions look very different, they are based on exactly the same ideas. I probably would not have posted anything if I had seen j0se's post before. Now it is done, I leave the post, it shows at least that, really, TIMTOWTDI in Perl.

(BTW, j0se, I have spent at least 18 weeks in your country, specifically in Bratislava, working for Orange Slovakia back in 2008 (preparing the Euro transition), and also 6 or 7 more weeks a few years before. And, long before, I also visited Bratislava as a young tourist back in 1975, in a totally different and quite difficult political context. Nice city and very nice people. Sorry for the off-topic digression.)