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);