Using your script on my Win32 box to connect to an SSH2 server on my linux box, I find that the connection is made without any trouble at all.
However, the 'scp_get' call segfaults, and I get the following error message:

libssh2_scp_recv(ss->session, path, &st) -> 0x2b849a4
[download]

If I try an 'scp_put' I get a similar message (and segfault):

libssh2_scp_send_ex(ss->session, path, mode, size, mtime, atime) -> 0x
+2b8a0d4
[download]

I find that the file I tried to upload with 'scp_get' was created in the correct location on the server ... but is empty :-(
The test script that ships with the Net-SSH2 source, constructs the 'scp_get' call a little differently (though that's not the problem, afaict). It does:

my $check = IO::Scalar->new;
$ssh2->scp_get($remote, $check);
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I hadn't realised scp wasn't working on Windows. (I failed to notice that, since IO::Scalar was not installed, the scp tests were being skipped.) OTOH, sftp seems to work fine
I'm using Net-SSH2-0.18 on perl-5.10.

Update: Just noticed that 'scp_put' and 'scp_get' both work ok for me on perl-5.8.8, Win32. If you're using Win32, and you really do need scp, then 5.8.8 is probably the simplest way to achieve it.

Cheers,
Rob