Hello bsherkhane,

As Anonymous Monk says, if this is a database question, then hashes aren’t needed.

However, if you do have two hashes and want to find their intersection, just remember that the keys of a hash are accessible as a list via the Perl built-in keys function. So you really want the intersection of two lists, and this is an FAQ: see perlfaq4#How-do-I-compute-the-difference-of-two-arrays?-How-do-I-compute-the-intersection-of-two-arrays?

Update: The logic is actually simpler with hashes: because each key can occur only once in a given hash, you only need to determine whether an entry corresponding to each key in the first hash exists in the second:

use strict;
use warnings;
use Data::Dump;

my %hash1 = ( a => 1, b => 2, c => 3, );
my %hash2 = ( b => 4, e => 5, f => 6, c => 7, );
my %intersection;

for my $key (keys %hash1)
{
    $intersection{$key} = [ $hash1{$key}, $hash2{$key} ]
        if exists $hash2{$key};
}

dd \%intersection;
[download]

Output:

18:00 >perl 1527_SoPW.pl
{ b => [2, 4], c => [3, 7] }

18:01 >
[download]

(Of course, you’ll have to decide what to do when the values differ. I’ve just included both values in an anonymous array.)

Hope that helps,

Alternatively, you could find just the keys shared by both hashes using grep

use v5.22;
use warnings;

my %hash1 = ( a => 1, b => 2, c => 3, );
my %hash2 = ( b => 4, e => 5, f => 6, c => 7, );


my @results = grep { exists $hash2{$_} } keys %hash1;

say join ',',@results;
#b,c
[download]

Also see perlfaq4, which adresses the problem of finding the common elements of two structures.