case on postgresql to insert/update table -

i using simple case condition insert or update on postgresql didnt know why when insert insert/update each condition got error..

this simple function:

create or replace function insert_new_table_log() returns trigger $new_table$ begin select id_hdr,     case id_hdr         when id_hdr = old.id                          (update new_table_dtl               set id_hdr = old.id, nama = old.nama,                  description=old.description               id_hdr = old.id)         else             (insert new_table_dtl(id_hdr, nama, description)               values(old.id, old.nama, old.description))     end     new_table_dtl; return new;  end; $new_table$ language plpgsql; 

and message error

error: syntax error @ or near "new_table_dtl" line 7: (update new_table_dtl set id_hdr = old.id, nama = old.na...