or download this
use Benchmark qw(cmpthese);
...
with_consthash_moddRA => sub { @h{'one','two'} = (8,1); my @r=with
+_hash(\%h); @h{'one','two'}=(); @r },
with_consthash_moddRS => sub { @h{'one','two'} = (8,1); my $r=with
+_hash(\%h); @h{'one','two'}=(); $r },
});