#!/usr/bin/perl -w
#
# Sample snipped, containing code taken from the 
# documentation for Parallel::ForkManager and 
# example 16.21 from the _Perl_Cookbook_.
#
use strict;
use vars qw($pm);
use Parallel::ForkManager;

#
# Maximum of 20 simultaneous processes,
# and begin graceful shutdown after 6 hrs.
#
my $MAX_PROCESSES = 20;
my $MAX_TIME = 6 * 3600;

$pm = new Parallel::ForkManager($MAX_PROCESSES) 
or die("Unable to create ForkManager object: $!\n");

#
# &load_data() subroutine defined elsewhere
#
my (@all_data);
@all_data = &load_data();

$SIG{ARLM} = sub { die("TimeOut"); };
eval {
    alarm($MAX_TIME);
    foreach my $data (@all_data) {
        my $pid = $pm->start and next;

        # Process or call processing routines 
        # for $data here

        $pm->finish;
    }
    $pm->wait_all_children;
    alarm(0);
};
if ($@) {
    if ($@ =~ m/TimeOut/) {
        $pm->set_max_procs(0);
        $pm->wait_all_children;
    }
    else {
        alarm(0);
        die;
    }
}