Well, part of the idea with Shell.pm is to avoid messing around with pipes altogether. (The rest of the idea seems to be Larry Wall goofing around -- see the pod.) You can write your example like this:

use strict;
use Shell;
my @out = ps('-u', 'gvc');
[download]

which will have the same result as if you'd opened a pipe to ps and slurped the contents into the @out array.

HTH