Altering your code to run as a standalone sample without needing access to a mail server and using threads (hence create rather than new) I get:

use warnings;
use strict;
use threads;
use Thread::Queue;

sub smtpblast{
    my $mdq= shift;
    my $pending= $mdq->pending;
    while ($pending > 0){
        my $md= $mdq->dequeue_nb;
        print "processing $md\n";
        sleep $md;
        $pending= $mdq->pending;
    }
    
    my $threadid = threads->self;
    print "\n The process for thread $threadid is finished!\n";
}

my $mdqueue=Thread::Queue->new();
$mdqueue->enqueue(10, 2, 5, 3, 7, 5);
my $thr1=threads->create (\&smtpblast, $mdqueue);
my $thr2=threads->create (\&smtpblast, $mdqueue);
my $thr3=threads->create (\&smtpblast, $mdqueue);
my $thr4=threads->create (\&smtpblast, $mdqueue);

$thr1->join;
print "\n Thread $thr1 joined! \n";
$thr2->join;
print "\n Thread $thr2 joined! \n";
$thr3->join;
print "\n Thread $thr3 joined! \n";
$thr4->join;
print "\n Thread $thr4 joined! \n";
[download]

which prints:

processing 10
processing 2
processing 5
processing 3
processing 7
processing 5

 The process for thread threads=SCALAR(0x3fdc57c) is finished!

 The process for thread threads=SCALAR(0x4508800) is finished!

 The process for thread threads=SCALAR(0x3ab0328) is finished!

 The process for thread threads=SCALAR(0x2534bbc) is finished!
Attempt to free unreferenced scalar: SV 0x2023ed0, Perl interpreter: 0
+x2018414 at C:\Documents and Settings\Peter\My Documents\PerlScratch\
+noname.pl line 22.

 Thread threads=SCALAR(0x201f7e8) joined! 
Attempt to free unreferenced scalar: SV 0x22c2318, Perl interpreter: 0
+x22bf014 at C:\Documents and Settings\Peter\My Documents\PerlScratch\
+noname.pl line 23.

 Thread threads=SCALAR(0x201f7f4) joined! 
Attempt to free unreferenced scalar: SV 0x383cc50, Perl interpreter: 0
+x3afc294 at C:\Documents and Settings\Peter\My Documents\PerlScratch\
+noname.pl line 24.

 Thread threads=SCALAR(0x201f800) joined! 
Attempt to free unreferenced scalar: SV 0x3d68e68, Perl interpreter: 0
+x3d65314 at C:\Documents and Settings\Peter\My Documents\PerlScratch\
+noname.pl line 25.

 Thread threads=SCALAR(0x201f80c) joined!
[download]

and terminates as expected despite the errors.

Can you generate a similar sample the demonstrates the problem you are seeing?

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.