I've got a code segment like this (for use on Win32):

.
.
my $ssh2 = Net::SSH2->new();

$ssh2->connect('xxx.xxx.xxx.xxx') or die;

$ssh2->auth_password('user','pass')
  or die "Unable to login $! \n";

my $chan1 = $ssh2->channel();

$chan1->blocking(1);

$chan1->exec('echo $PATH');
$chan1->read($buf, $buflen);
print "BUF: $buf\n";

$chan1->close;
.
.
[download]

You might see if there's anything there that helps.

Cheers,
Rob