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";
}
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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";
}
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thanks a lot ikegami....your suggestion worked beautifully..!!

I am just new to perl so facing all such kind of problems.

In addition of above similar problem one more doubt i want u to clear...

    if I want to enqueue arrays executed by $sth->fetchrow in a queue for the usage of same queue to later purpose then what should i do means how to get reference of executed rows from result set ??

Did you want each row to be a different queue item?

while (my $row = $sth->fetch()) {
    # Must copy since fetch reuses array.
    $row = [ @$row ];

    $q->enqueue(share($row));
}
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You will be using threads right? Otherwise a queue is simply:

my @queue;

# Put stuff in
while (...) {
    push @queue, ...;
}

# Take stuff out
while (@queue) {
    my $item = shift(@queue);
    ...
}
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