#!/usr/bin/perl
use strict;
use warnings;
use autodie;

my $num_jobs=4;

# Split the work up
open my $IFH, '<', 'data.inp';
my @OFH;
open $OFH[$_-1], '>', "data.$_" for 1 .. $num_jobs;
my $cnt=0;
while (<$IFH>) {
    ++$cnt;
    my $FH = $OFH[$cnt%$num_jobs];
    print $FH, $_;
}
close $OFH[$_-1] for 1 .. $num_jobs;

# Do the work
for my $j (1 .. $num_jobs) {
    `perl orig_do_job --infile=data.$_ --outfile=data.out.$_  & `;
}

# Collect the results
`cat data.out.* >data.out`;