CREATE OR REPLACE FUNCTION blah_insert_trigger()
RETURNS TRIGGER AS $$
BEGIN
 IF ( NEW.blah = 'a') THEN INSERT INTO matable_a VALUES (NEW.*);
 ELSE IF (NEW.blah = 'b') THEN INSERT INTO matable_b VALUES (NEW.*);
 ELSE INSERT INTO matable VALUES (NEW.*);
    END IF;
    RETURN NULL;
END;
$$
LANGUAGE plpgsql;

ERROR:  syntax error at or near ";"
LINE 22: END;