I can't comment on which is better (fork/threads), but here's an example using Parallel::ForkManager that I wrote a while ago for someone else.

I've modified it a bit to suit your requirements. First, $max_forks specifies the maximum number of forks to run at a time. Next, I create an array of 1000 elements. Then in the while(), I splice out 200 elements of the @array into a new array, and fork out to db_save() with that array slice, simulating your desire to only do a specific number of items per fork().

#!/usr/bin/perl

use warnings;
use strict;

use Parallel::ForkManager;

my $max_forks = 3;

my $fork = new Parallel::ForkManager($max_forks);

my @array = (1..1000);

# on start callback

$fork->run_on_start(
    sub {
            my $pid = shift;
    }
);

# on finish callback

$fork->run_on_finish(
    sub {
        my ($pid, $exit, $ident, $signal, $core) = @_;
        if ($core){
            print "PID $pid core dumped.\n";
        }
    }
);

# forking code


while (@array){

    my @chunk = splice @array, 0, 200;

    $fork->start and next;

    sleep(2);
    db_save(@chunk);

    $fork->finish;

}

sub db_save {
    my @a = @_;
    print "$a[1]\n";
}

$fork->wait_all_children;
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