Update: Just realized this is the very same as LanX above - DB<105> etc. was confusing me.

This may help, and will allow you to merge as many hashes as you wish:

use strict;
use warnings;
use Data::Dumper;

my %hash1 = (
    "key1" => 1,
    "key15" => 3,
    "key150" => 1
);
my %hash2 = (
    "key1" => 1,
    "key15" => 1,
    "key140" => 1
);
        
my %merged;
$merged{$_} += $hash1{$_} for keys %hash1;
$merged{$_} += $hash2{$_} for keys %hash2;

print Dumper(\%merged);
[download]

Output:

$VAR1 = {
          'key15' => 4,
          'key140' => 1,
          'key1' => 2,
          'key150' => 1
        };
[download]