#!/usr/bin/perl
use strict;
use warnings;
use Benchmark qw/cmpthese/;

my %hash;
my &#36key="foo";

cmpthese (-10, {
    ohne  => sub { &#36hash{&#36key}=0; &#36hash{&#36key}++ for 0 .. 1_000_000; },
    mit   => sub { &#36hash{"&#36key"}=0; &#36hash{"&#36key"}++ for 0 .. 1_000_000; },
});

Benchmark: running mit, ohne for at least 10 CPU seconds...
       mit: 11 wallclock secs (10.36 usr +  0.01 sys = 10.37 CPU) @  0.87/s (n=9)
      ohne: 11 wallclock secs (10.12 usr +  0.02 sys = 10.14 CPU) @  2.66/s (n=27)
     s/iter  mit ohne
mit    1.15   -- -67%
ohne  0.376 207%   --