my %data = (
    ettablenr => '2',
    etcell2x1 => 'Task',
    etcell2x2 => '1',
    etcell2x3 => '2',
    etcell2x4 => '3',
    etcell2x5 => 'High',
    etcell2x6 => 'CSS',
    etcell2x7 => 'CCCC',
    etcell2x8 => 'Twiki Updation',
    etcell3x1 => 'Task',
    etcell3x2 => '4',
    etcell3x3 => '5',
    etcell3x4 => '6',
    etcell3x5 => 'High',
    etcell3x6 => 'DSS',
    etcell3x7 => 'DDDD',
    etcell3x8 => 'Twiki CSV',
    etrows    => '3',
    etsave    => 'Save table'
);

# you change something with $data{etrows} = 4; 

my $res = $ua->request(POST $url,
  Content_Type=>'form-data',
  Content =>[ %data ]
);