If you are accessing the database from a windows machine then DBD::ODBC is all you need.
in reply to SQL Server
For unix systems I recommend using DBD::ODBC with freetds and iodbc. That combination provides support for bound parameters, which DBD::Sybase with freetds does not if I recall correctly.
Here is the installation script I used last year to install that combination:
Re: Accessing Microsoft SQL Server from Linux using DBD::ODBC
There is also an excellent guide on working with DBD::Sybase here:
Accessing Microsoft SQL Server from Linux using DBD::Sybase