Question

I am pretty new to Perl and need to accomplish a task quickly. Any help is appreciated!

I have two hash of arrays as follows:

Hash 1
-------
w: ['A','B','C']
e: ['P','Q','R']

Hash 2
-------
w:['A','B','C']
e:['P','Q','O']
r:['S','T']

Context:

1. I want to find the differece in values for same keys(e.g Hash 1 does not have
   value ‘O’ from Hash 2 for the same key ‘e’.

2. Find the difference in keys. (e.g ‘r’ is not present in hash 1.

I put together some code but it checks the exact value of the complete line from two hashes. For example If I have ‘A’,’B’,’C’ in hash 1 for key w and ‘B’, ‘C’,’A’ in hash 2 for same key if flags a difference. I want to compare value by value-

Following code compares two hash os arrays. So from the above example A,B,C from hash 1 is not equal to B , A,C from hash 2. However I want to check the existence of the individual item say A in and not worry about the order.

for ( keys %hash2 ) 
{     
    unless ( exists $hash1{$_} ) # Checks for mismatches in keys
    {         
        print "$_: Key mismatch $_ received \n"; 
        next;     
    }      

    if ( $hash2{$_} eq $hash1{$_} ) #Compares two lines exactly         
    {        
        print "$_: No mismatch \n";  
    }     
    else 
    {       
        print "$_: Value mismatch for key $_ \n";  #Difference in Value
    } 
} 

Answer 1

If you don’t care about orders, just compare the ordered set of values:

your code:

if ( $hash2{$_} eq $hash1{$_} ) #Compares two lines exactly      

Should be:

if (     join(",", sort @{ $hash1{$_}})
      eq join(",", sort @{ $hash2{$_}}) ) #Compares two lines exactly      

---

On the other hand, if you want to compare memberships of arrays, simply turn array into a hashref:

foreach my $key2 ( keys %hash2 ) {
    unless ( exists $hash1{$key2} ) { print ""; next; };

    my %subhash1 = map { ( $_ => 1 ) } @{ $hash1{$key} };
    my %subhash2 = map { ( $_ => 1 ) } @{ $hash2{$key} };

    # Compare 2 subhashes same way you are comparing parent hashes in inner loop

    foreach my $subkey2 ( keys %subhash2 ) {
        # Check for exists
        ...
    }
}