Thank you all for your reply, I found it very helpful. However, when I mention about having 4 system calls that resulted in 4 pids, I mean the following(having them runnning in background): 
my $cmd = "process_file -c arg1 -d arg2";
for(1..40)
{
    if(!WINDOWS)
    {
        system("$cmd > /dev/null &");
    }
    else
    {
        system("sh -c \"$cmd > /tmp/null \"&");
    }
}

[download]
as you can see, the above code will gives me 4 processes running in the back ground, but I have no control over those pids

In reply to Re: How do you get PID of a program called using system call? by monk_e_magic
in thread How do you get PID of a program called using system call? by monk_e_magic

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