use strict;
use warnings;
no warnings 'void';
use threads;

use Thread::Barrier   qw( );
use Time::HiRes       qw( time );

use constant NUM_THREADS => 4;

my $t = time;

my $barrier1 = Thread::Barrier->new( NUM_THREADS + 1 );
my $barrier2 = Thread::Barrier->new( NUM_THREADS );

my @t = map async {
    my $id = threads-> tid - 1;

    # Wait for main thread to complete.
    $barrier1->wait;

    sin for 1 .. 1e7;
    
    printf "first, %d %.3f\n", $id, time - $t;

    # Wait for all threads to reach here.
    $barrier2->wait;

    printf "next,  %d %.3f\n", $id, time - $t;
}, 1 .. NUM_THREADS;

sin for 1 .. 1e7;

$barrier1->wait;

$_->join for @t;