Does this do what you want:

use Net::SSH2;
use warnings;
use strict;

my $buflen = 100;
my $buf = '0' x $buflen;

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

$ssh2->connect('IP Address') or die;

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

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

$chan1->blocking(1);

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

$chan1->close;

__END__
[download]

That works fine for me on Windows with perl 5.8.8. (The script you posted did not.) But it segfaults on perl 5.10.0 on Windows. (There are issues with Net::SSH2 on perl 5.10 ... and not just windows issues. See eg http://rt.cpan.org/Ticket/Display.html?id=36071.)

Cheers,
Rob