As stated on the module documentation, to report bugs or ask for new features or help, please, mail me (the author) or use the CPAN bug tracking system.
Perlmonks is also a good place to get help.
SSH2_FX_xxx are low level protocol error codes and so, meaningless for high level methods suchs as get or put. Anyway, you can get the result for the last protocol interaction from $sftp->status