This isn't what you want, but it is what you have asked for. And it is rather less cumbersome than Thread::Pool:

#! perl -slw
use strict;
package pool;
use threads;
use Thread::Queue;

sub new{
    my $class = shift;
    my $nThreads = shift;
    my $Qin = new Thread::Queue;
    my $Qout = new Thread::Queue;
    my @threads = map{
        threads->new(
            sub {
                my( $Qin, $Qout ) =  @_;
                while( my $code = $Qin->dequeue() ) {
                    $Qout->enqueue( eval $code );
                }
            }, $Qin, $Qout
        )
    } 1 .. $nThreads;
    return bless [ $Qin, $Qout, \@threads ], $class
}

sub job {
    my( $Qin, $Qout, $threads ) = @{ +shift };
    $Qin->enqueue( shift );
    return;
}

sub DESTROY {
    my( $Qin, $Qout, $threads ) = @{ +shift };
    $Qin->enqueue( undef ) for @$threads;
    sleep 0;
    $_->join for @$threads;
}

*stop = *stop = *DESTROY;

package main;

my $pool = pool->new( 5);

for ( 1 .. 1000 ) {
    $pool->job( qq[ 
        sleep 5; 
        printf "In thread(%d). arg:%d\n", threads->tid, $_
    ] );
}
sleep 10;
$pool->stop;

__END__
c:\test>543977
In thread(1). arg:1
In thread(2). arg:2
In thread(3). arg:3
In thread(4). arg:4
In thread(5). arg:5
In thread(1). arg:6
In thread(2). arg:7
In thread(3). arg:8
In thread(4). arg:9
In thread(5). arg:10
In thread(1). arg:11
In thread(2). arg:12
In thread(3). arg:13
In thread(4). arg:14
In thread(5). arg:15
In thread(4). arg:16
In thread(3). arg:17
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