Okay, not gonna give away anything big here, and looking at the ocede the way it is is difficult (you should use the code tags around your code).

$cmd = ;

should be $cmd = <STDIN>;
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You should also check right from the start if there are more than 3 commands, and drop out right then and there.

if ($max > 3) {
    print "exiting \n";
    exit(1);
}
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I know this isn't TOO much help, but it is homework. and IMHO pipes are a lot of fun to play with and figure out on your own. You can do a lot of really slick stuff with them. but if someone tells you how to do it, you lose the fun of figuring it out ... and you won't learn them as well.

just skim though the cookbook, it gives you everything you need to work on this project if i remember correctly.

mbond