Hope I understand what you said. I did something on windows, as I don't have unix around today, sweet home, but you can easily move this to unix. I tested the following code with: 
type a.pl|perl -w a.pl
and it demonstrates how you can make your scripts to follow the behavior of tranditional pipe, and take output from another process as input. 
a.pl:
@in = <STDIN>;
foreach (@in) {
    print "from perl script: ", $_;
}

[download]
Update 2: I don't know whether you have control towards cmd1, cmd2, etc. or not. If yes, I would strongly suggest you to use pipe(), to help you connect those handlers into pairs.

Update: Hm...Now I know what you mean, so you want your script to act as the "middle man". Anyway, I still would like to leave my original reply there, as it is still a good answer to "the question I thought it was".

Your approach ALONE sounds good to me, but that while loop can be simplified, and you may borrow the concept from following code: 
open(DATA, "<", "ex902.pl");
@in = <DATA>;#read in as array
close(DATA);
open(DATA1, ">", "data.txt");
print DATA1 @in;#flush the whole array out
close(DATA1);

[download]
However I am wondering why you are trying to do that. It sounds to me, like you are reinventing something the OS is doing for you. For the project you are working on, is there an alternative solution, which allows you to utilize your OS as much as possible? Well, any way, I believe that you must have a good reason to do this.

In reply to Re: Robustly piping several processes. by pg
in thread Robustly piping several processes. by BazB

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