my %hash3 = (%hash1, %hash2);
my @uniq  = keys %hash3;

##</code><code>##

my @uniq = keys (%hash1, %hash2);

##</code><code>##

#! perl
use Modern::Perl;
use Data::Dump;

my %hash1 = (fred  => 'wilma', barney => 'betty');
my %hash2 = (homer => 'marge', fred   => 'wilma');
my @uniq  = keys { %hash1, %hash2 };
dd @uniq;

##</code><code>##

23:05 >perl 464_SoPW.pl
("barney", "homer", "fred")

23:08 >