So you want to go through hash1 and separate what's common from what's unique. Then you want to find the unique things in hash2.

my (@common, @uniq1, @uniq2);
for (keys %hash1) {
  if (exists $hash2{$_}) {
    push @common, $_;
    delete $hash2{$_};  # All that will be left in hash2 is what wasn'
+t in hash1
  }
  else { push @uniq1, $_ }
}
@uniq2 = keys %hash2;
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