perl - Net::Google::Spreadsheets 500 error, what am I doing wrong?

Question

I'm trying to use Net::Google::Spreadsheets to manipulate a Google Docs spreadsheet (side note: you may have seen my previous question where I was trying to work from the inside of Google Docs, now I'm trying a different angle)

I'm trying an example pretty much straight out of the perldoc:

     #!/usr/bin/perl
     use strict;
     use warnings;
     use Net::Google::Spreadsheets;

     my $service = Net::Google::Spreadsheets->new(
       username => 'my.email@gmail.com',
       password => 'mypassword'
     );

     my @spreadsheets = $service->spreadsheets();

     # find a spreadsheet by key
     my $spreadsheet = $service->spreadsheet(
       {
          title => 'Perl Test' # This is a spreadsheet I manually created already
       }
     );

     # find a worksheet by title
     my $worksheet = $spreadsheet->worksheet(
       {
           title => 'Sheet1'
       }
     );

     my $cell = $worksheet->cell({col => 1, row => 1});

     # update input value of a cell
     $cell->input_value('new value');

When I run my code, I get this error:

    request for 'https://spreadsheets.google.com/feeds/worksheets/tNdoUPkz7MhRAtVoBaaZVHQ/private/full?title=Sheet1' failed:
    500 Internal Server Error
    Internal Error
     at /usr/local/share/perl/5.10.1/Net/Google/DataAPI/Role/Service.pm line 96
    Net::Google::DataAPI::Role::Service::request('Net::Google::Spreadsheets=HASH(0x167ce60)', 'HASH(0x1c63ba8)') called at /usr/local/share/perl/5.10.1/Net/Google/DataAPI/Role/Service.pm line 158
    Net::Google::DataAPI::Role::Service::get_feed('Net::Google::Spreadsheets=HASH(0x167ce60)', 'https://spreadsheets.google.com/feeds/worksheets/tNdoUPkz7MhR...', 'HASH(0x1a38d58)') called at /usr/local/share/perl/5.10.1/Net/Google/DataAPI.pm line 106
    Net::Google::Spreadsheets::Spreadsheet::worksheets('Net::Google::Spreadsheets::Spreadsheet=HASH(0x1a36460)', 'HASH(0x1a38d58)') called at /usr/local/share/perl/5.10.1/Net/Google/DataAPI.pm line 119
    Net::Google::Spreadsheets::Spreadsheet::worksheet('Net::Google::Spreadsheets::Spreadsheet=HASH(0x1a36460)', 'HASH(0x1a38d58)') called at spreadsheet_test.pl line 22

And then if I try to open up the Perl Test spreadsheet from within Google Docs, Google itself gives me the equivalent of a 500 error.

So what am I doing wrong?