Getting SHARED BY property of a task

System

How can I get the "shared by" property of a workflow task using Perl? Below is the code I am using which runs (although
there is no GetSharedBy property defined in the perldocs- probably it is undocumented) but this just returns an empty string. What is the correct way of doing this? Thanx.
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my $task = new TeamSite::WFtask($id);

if ($task->IsValid())
{
my $sharedby = $task->GetSharedBy();
print "Shared By: ".$sharedby."\n";
}