Unfortunately, you can't access the lexical hash variable from a string-evaled code in Benchmark, so the benchmarks measures nothing.

#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

use Benchmark qw{ cmpthese };

my %hl;
@hl{1001 .. 2000} = (1) x 1000;
our %hg = %hl;
our ($el, $vl, $eg, $vg) = (0) x 4;

die unless $hl{1001};
die unless $hg{1001};

cmpthese(-1, {
    exist_l => q{ ++$el if exists $hl{1001} },
    value_l => q{ ++$vl if $hl{1001} },
    exist_g => q{ ++$eg if exists $hg{1001} },
    value_g => q{ ++$vg if $hg{1001} },
});

say join "\n", "el: $el", "vl: $vl", "eg: $eg", "vg: $vg";
[download]

5.26.1 on Linux:

              Rate value_g exist_g value_l exist_l
value_g 17625636/s      --     -4%    -47%    -53%
exist_g 18303545/s      4%      --    -45%    -51%
value_l 33363781/s     89%     82%      --    -11%
exist_l 37417325/s    112%    104%     12%      --
el: 0
vl: 0
eg: 23229990
vg: 23229990
[download]

Blead gives smaller differences, but the order is the same.

Update: Changing q{ to sub { changes the order randomly and makes the difference less than 10%.

Update 2: Changing 1001 to 2001 in the benchmarked code (i.e. testing non-existent key) changes the differences to 20% and less, e.g.

              Rate value_g exist_g value_l exist_l
value_g 31977080/s      --     -2%     -8%    -19%
exist_g 32733979/s      2%      --     -6%    -17%
value_l 34737228/s      9%      6%      --    -12%
exist_l 39658833/s     24%     21%     14%      --
[download]

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