There are many cases where you use a variable that's not defined, out of scope, or not what you think ($key is not a hashref). Luckily you can find all those mistakes by applying three simple rules:

• Add use strict; and use warnings; at the top of your file. Perl will now tell you about those mistakes.
• Declare your variable with my. This way perl can tell when you've made a typo in a variable's name.
• Avoid single letter names, especially $a, which has a special value (some built-ins may use and change it (like sort), and perl won't warn you if you forgot to declare it). $x and $y may be an exception because they are pretty explicit, but only when they are used as coordinates.

Avoid single letter names

And i learned never to name my subroutines s Re^2: Can this be explained in layman's terms?

if you add use strict; use warnings; i bet you get enough clues to figure it out yourself!

hint %$key

and Reaped: Findidng Difference between two hash of arrays

and Reaped: Difference of Hash

anyway take a look at Data::Compare and to this old thread: Comparing hashes without sorting the keys

L*

Hello Nansh,

It seems that you are doing your first steps in Perl just now. It would be very good for you to always use strict and warnings.

Now regarding your question, since I got the opportunity to answer on your previous question (Findidng Difference between two hash of arrays), I start to wonder if you really want to use Hashes of Arrays or simple perldata (hash/Subscripts).

When you have a hash you do care about the sequence of the keys in the hash, as long as you have the key you can compare keys. I think in you case you want to compare the fruits and find the difference. If this is the scenario (assuming because your description and approach is not clear) it can be done like this:

#!/usr/bin/perl
use warnings;
use strict;
use Hash::Diff qw( diff );
use Data::Dumper qw(Dumper);

my %hash;
my @fruits = ("Fruit","Fruit1","Fruit3","Fruit4");
my @fruit_names = ("apple", "orange", "strawberry", "grape");

my @fruits_2 = ("Fruit","Fruit1","Fruit3","Fruit4");
my @fruit_names_2 = ("apple", "orange", "strawberry", "grapes");

# Approach one creating hash with 2 arrays
for (0..$#fruits) {
    $hash{$fruits[$_]} = $fruit_names[$_];
}

# print Dumper \%hash;

# Approach two creating hash with 2 arrays
my %hash_2;
@hash_2{@fruits} = @fruit_names;

# print Dumper \%hash_2;

my %hash_3;
@hash_3{@fruits_2} = @fruit_names_2;

# print Dumper \%hash_3;

my %hash_diff = %{ diff( \%hash_3, \%hash_2 ) };

print Dumper \%hash_diff;

__END__

$ perl test.pl
$VAR1 = {
          'Fruit4' => 'grapes'
        };
[download]

Obviously the two hashes contain the same names and fruits apart from the plural on the second hash.

I hope this helps more.