cmpthese -1, {
    shared => q[ 
        my %h : shared = 1..10;                   ++$h{ 1 }   for 1 .. 1e4 
    ],
    shared_locked_hv => q[ 
        my %h:shared   = 1 .. 10; do{ lock( %h ); ++$h{ 1 } } for 1 .. 1e4 
    ],
    non_shared    => q[ 
        my %h          = 1 .. 10;                 ++$h{ 1 }   for 1 .. 1e4 
    ],
};;
                  Rate shared_locked_hv           shared       non_shared
shared_locked_hv 145/s               --             -59%             -60%
shared           353/s             144%               --              -1%
non_shared       358/s             147%               1%               --