Thanks for this. The interesting thing is that if I stringify the code to avoid the sub call then I can replicate the ordering from my original post.

I added a false value to get a sense of the cost of the increment operation. value_true is value from your version, and is obviously faster as it does less work.

use warnings;
use strict;
use Benchmark qw{ cmpthese };

my %h;
@h{1001 .. 2000} = (1) x 1000;
my ($e, $vt, $vf) = (0) x 3;
$h{1002} = 0;

cmpthese(-2, {
    exist => sub { for (0..999_999) {   ++$e if exists $h{1001}   } },
    exist_str   => 'for (0..999_999) {   ++$e if exists $h{1001}  }',
    value_true  => sub { for (0..999_999) {   ++$vt if $h{1001}   } },
    value_str   => 'for (0..999_999) {   ++$vt if $h{1001}   }',
    value_false => sub { for (0..999_999) {   ++$vf if $h{1002}   } },
});

__DATA__
              Rate       exist  value_true   exist_str   value_str val
+ue_false
exist       16.1/s          --         -9%        -23%        -26%    
+    -27%
value_true  17.7/s         10%          --        -15%        -18%    
+    -20%
exist_str   20.9/s         29%         18%          --         -4%    
+     -6%
value_str   21.7/s         34%         22%          4%          --    
+     -2%
value_false 22.1/s         37%         25%          6%          2%    
+      --

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In reply to Re^3: "exists $hash{key}" is slower than "$hash{key}" by swl
in thread "exists $hash{key}" is slower than "$hash{key}" by swl

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