Does PostgreSQL have an UPDATE Function like UNIFY?

I was wondering if PostgreSQL had a function that allowed you to update a
table from a delimited file that would update matching records and insert
new records. Under Unify you could do an update with a switch (I think it
was -n) that would take input from a pipe delimited file (in the order the
fields of the table) and since the table had which field was unique it
would key on that and if it didn't find the key it would add the record. 
I have a table that has approximately 2500 records. The data for this table
(and other tables in the db) comes out of a system I manage that will
sometime in the future be transferred fully to this. So the data is updated
(dumped from the COBOL Indexed file) and then loaded into the table (about
once a week). I can delete the records and then add them but I think that
might be a bit time consuming.Will I have to write a C program or Perl script to do this? I am hoping
not. One can only dream. Thanks in advance.

John J. Boris, Sr.   Boris Computer Services/ONLine Services
email:john.boris@onlinesvc.com.com
bbs: The Bleeding Edge 609-858-9221