It's waiting for more stuff to be added to the queue.

If the queue is preloaded and doesn't change, you could use dequeue_nb.

use strict;
use warnings;

use threads;
use threads::shared;

use Thread::Queue;

my @ary :shared = qw( a b c );

my $q = Thread::Queue->new();
$q->enqueue(\@ary);

while (my $ar1 = $q->dequeue_nb()) {
    print "array reference : $ar1\n@$ar1\n";
}
[download]

If data will be added to the queue once the threads have started, use a special value to indicate there is no more data forthcoming. undef would work fine if your queue otherwise contains arrays.

use strict;
use warnings;

use threads;
use threads::shared;

use Thread::Queue;

my @ary :shared = qw( a b c );

my $q = Thread::Queue->new();
$q->enqueue(\@ary);
$q->enqueue(undef);  # One for each consumer.

while (my $ar1 = $q->dequeue()) {
    print "array reference : $ar1\n@$ar1\n";
}
[download]

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