my %results= (
    nothing => nothing(),
    _undef  => _undef(),
    empty   => empty(),
    zero    => zero(),
);

##</code><code>##

{   "nothing" => "_undef",
    "" => "empty",
    "zero" => 0,
}

##</code><code>##

    _undef:  11,363,636.36/s
     empty:   9,174,311.93/s
   nothing:  20,000,000.00/s
      zero: 166,666,666.67/s

##</code><code>##

sub nothing { return (); }
nothing() for 0..100_000_000;
warn time()-$^T;