use Class::CSV;

my $csv = Class::CSV->new(
  fields         => [qw/userid username/]
);

$csv->add_line([2063,'testuser']);
$csv->add_line({
  userid   => 2064,username => 'testuser2'
});

$csv->print();

# 2063,testuser
# 2064,testuser2

编辑：对于更多的库，您可以使用search CPAN。