Another solution: 
++$any{$_}
   for
      keys(%hash1),
      keys(%hash2),
      keys(%hash3),
      keys(%hash4);

for (keys(%test_hash)) {
   print("$test_hash{$_}\n")
      if !$any{$_};
}

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In reply to Re: Check if a key exists in several hashes at once by ikegami
in thread Check if a key exists in several hashes at once by Anonymous Monk

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