Concatenate table name in Pl/Pgsql

Today i m creating a function that includes dynamic concatenation of a partitioned table name as below :-

test=# CREATE OR REPLACE FUNCTION tmp_trigger_function()
test-# RETURNS TRIGGER AS $$
test$# DECLARE
test$# tbl_name text;
test$# abc varchar;
test$# BEGIN
test$# tbl_name := 'tmp';
test$# select to_char(NEW.a::timestamp,'yyyymmdd') into abc ;
test$# insert into tmp || abc values ( NEW.* );
test$# RETURN NULL;
test$# END;
test$# $$
test-# LANGUAGE plpgsql;
ERROR:  syntax error at or near "||"
LINE 9: insert into tmp || abc values ( NEW.* );
                        ^
Time: 0.901 ms
test=#
test=#