#!/usr/bin/perl
    use utf8;
    use feature qw( say );
    use threads;
    use threads::shared;
    use Data::Dumper;
    use Storable qw ( freeze thaw );

    my $Clock = threads-> new(
        {'context' => 'void'},
        sub {
            my $count = 0;
            while(1){
                say "programs implemented {$count} sec";
                sleep 1;
                $count += 1;
            }
        }
    );

    my $LockVar :shared;
    $LockVar = "default";
    my $LockArray :shared;
    $LockArray = qw( You cannot lock the individual elements of a container variable );
    $Lock3Sec = threads->new(
        {'void' => 'void'},
        sub {
            {
                say "the lock var default value is {$LockVar}";
                lock($LockVar) or warn "cannot lock the var because {$!}\n";
                sleep 3;
                say $LockVar;
            }
        },
    );


    $TryToReadLockVar = threads->new(
        {'void' => 'void'},
        sub {
            my $count = 1;
            LINE:    while( $LockVar eq 'default'){
                say "try to modify the Lock var {$count} time";
                $count += 1;
                $LockVar = 'this lock var has been change' or redo LINE;
                say "modify done";
            }
        },
    );

    $TryToReadLockVar->join();
    $Lock3Sec->detach();
    $Clock->detach();

    sleep 3;

##</code><code>##


    programs implemented {0} sec
    the lock var default value is {default}
    try to modify the Lock var {1} time
    modify done
    programs implemented {1} sec
    programs implemented {2} sec
    programs implemented {3} sec
    this lock var has been change