in reply to
Perl and Database
Informix, Oracle or SQL Server? ... help me to sale myself in future
Technically I would go with PostgreSQL, but that is not in your list and it would not help sale yourself as much as it should. The sad fact is that recruiters do not see generic DB knowledge as they should and look for keywords like Oracle or SQL Server - it is not uncommon for non-technical people not to know the difference between SQL and MS SQL Server.
It pains me to say this, but for saleability you should go for Oracle or MS SQL Server. It is difficult to call which of those will have the most secure future.