Copy command and duplicate items (Support Replace?)

Hi,

Writing a script to pull data from SQL server into a flat-file (or just
piped in directly to PG using Perl DBI)

Just wondering if the copy command is able to do a replace if there are
existing data in the Db already. (This is usually in the case of updates
to specific rows and there be a timestamp indicating it has been changed
etc.)

In MySQL, the mysqlimport util has the --replace function which will
replace the data if there is any event of a duplicate.

Does PG support this?