fork is the easy answer, but your forking loop isn't quite right. You will always end up spawning two processes, because both the parent and the child exec within the loop. Try 
for my $x (1..$total_number_of_runs) {
    my $pid = fork;
    if (not defined $pid) {
        die("Unable to create child process: $!\n");
    }
    exec("shell_script < $input_file") unless $pid; #thanks, bluto
}

[download]
The parent launches all the children, then exits.
Caution: Contents may have been coded under pressure.

In reply to Re: Is fork() my answer to using dual-cpu? by Roy Johnson
in thread Is fork() my answer to using dual-cpu? by axl163

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