I'm new to this whole IPC thing, so please bear with me...

I need to run the same external executable 100 times with slightly different parameters, and I can only have 5 instances running at a time (not counting the initiating Perl script).

Here's my code: 

$counter    =    0;
$pid_count    =    0;

do {
    if ($pid_count < 5) {
        ++$counter;
        ++$pid_count;
        if (!defined($$counter = fork())) { ## <---This is line 175
            warn "Unable to fork $counter: $!";
            }
        elsif ($$counter == 0) {
            print "Running this command line: $cmd[$counter]\n";
            exec("$cmd[$counter]");
            warn "Can't exec $cmd[$counter]: $!";
            }
        else {
            waitpid($$counter, 0);
            --$pid_count;
            }
        }
    } until ($counter == $max_frag_id);

[download]

When I run this, I get the following error message: Modification of a read-only value attempted at script.pl line 175.

What does this mean and how do I fix it?

Many thanks!

Kevin J.

In reply to Forking 100 processes, 5 at a time by nagan

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