Maybe this example might help a bit (from the Perl Cookbook):

use IPC::Open2;

open2(*README, *WRITEME, $program);
print WRITEME "here's your input!\n";
$output = <README>;

close(README);
close(WRITEME);
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You can either use typeglobs as used above, or you can use self-made IO::Handle objects and pass them in, as the open2 function will not create handles for you.

Note that you do not need to use die with the open2 function, as it dies on error. If you need to know if it produced an error, wrap it in an eval block and test $@.

I think IPC::Open3 module's args are different, and check out the IPC::Open2 and IPC::Open3 documentation for more detailed information.