prelude: |
  hash1 = 1_000_000.times.to_h { [rand, true]}
  hash2 = hash1.dup
  hash2.keys[1..100_000].each { hash2.delete _1 }
  hash2.delete hash2.first[0]

benchmark:
  hash1: hash1.first
  hash2: hash2.first

loop_count: 100_000