it didn't occur to me that the threads were actually sharing the FILE filehandle , so if one acquired the lock , each of them actually acquired the lock because FILE was shared amongst them( thanks tye for pointing that out )

I managed to pull of a quick replacement for that which works as one would expect.

Notice the 9-$x , that is to make sure that time(thread1)>time(thread2)>time(thread3)>... .

Also notice that $thread_lock are thread-specific locks 

use strict;
use warnings;
use threads;
use feature 'say' ;
use Fcntl qw(:flock);
my $file_path = ">>/tmp/test.txt";
open(FILE, $file_path);

for(0..9) {
    threads->new(\&worker, $_);
}

$_->join for threads->list;

sub worker {
    my $x = shift;
    my $locked;
    open(my $thread_lock,$file_path);
    $locked = flock($thread_lock, LOCK_EX|LOCK_NB );
    if( $locked ) {
        say "$x: lock acquired";
        sleep 9-$x;
    } else {
        say "$x: cannot acquire lock";
    };

    if($locked) {
        flock( $thread_lock, LOCK_UN );
        print "$x: lock released\n";
    }
    return;
}

[download]
0: lock acquired
1: cannot acquire lock
2: cannot acquire lock
3: cannot acquire lock
4: cannot acquire lock
5: cannot acquire lock
6: cannot acquire lock
7: cannot acquire lock
8: cannot acquire lock
9: cannot acquire lock
0: lock released

[download]

In reply to Re^3: Slow worker threads by spx2
in thread Slow worker threads by pome23

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