#! perl -slw
use strict;
use threads;
use threads::shared;
use List::Util qw[ shuffle ];
use Time::HiRes qw[ time ];

our $N //= 1e3;
our $W //= 20;
our $L //= 1;

my %counts :shared;

sub worker {
    my @order = shuffle 1 .. 20;
    for( 1 .. $N ) {
        $L and lock %counts;
        ++$counts{ $_ } for @order;
    }
}

my $start = time;
$_->join for map threads->new( \&worker ), 1 .. $W;
my $end = time;

for( sort{ $a <=> $b } keys %counts ) {
    printf "%2u : %u\n", $_, $counts{ $_ };
}

printf "Took %.6f seconds\n", $end - $start;