nextval/dbi question

hey.

i'm using dbi in perl to access a table whos primary key is a serialized
variable. i want to preform an insert on the table and i want the value of
the key associated with that insert.

this is what i'm doing:
# i get the new value like this:
select nextval('testtable_the_key_seq');

#and then i preforme the insert like this:
insert into testtable (an_id, timestamp) values (2, 2);

what results.

say the last value of  the sequence is 'n-1' so the select nextval
statement above will return 'n' but when i preform the insert the value of
testtable.the_key is actually 'n+1'. should i wrap the insert up into a
transaction? any help would be most appreciated.

i dont know if this is relevent but in perl i'm preparing the statement by
using (?,?) and place holders for the (2,2).

thanks
john