DB<1>  @keylist = qw/one two three four/;

  DB<2>  $hash = ();

  DB<3>  sub make_hash {$string = join '}{', @_ ; $string =  '$hash{' . $string . '} = 0'; eval $string;}

  DB<4> make_hash(@keylist);

  DB<5> x \%hash;
0  HASH(0x6004f9dc0)
   'one' => HASH(0x6004f9d48)
      'two' => HASH(0x6004f9c10)
         'three' => HASH(0x6004f9be0)
            'four' => 0

  DB<6> make_hash( qw/jan feb mar apr may jun/)

  DB<7> x \%hash;
0  HASH(0x6004f9dc0)
   'jan' => HASH(0x60064b430)
      'feb' => HASH(0x60064b508)
         'mar' => HASH(0x60064b538)
            'apr' => HASH(0x600500860)
               'may' => HASH(0x60064eab0)
                  'jun' => 0
   'one' => HASH(0x6004f9f58)
      'two' => HASH(0x600639458)
         'three' => HASH(0x6006175e8)
            'four' => 0