mariadb – What is the correct way to declare and use MarisDB user defined variables?

I’m using MariaDB version 10.3.28-MariaDB-cll-lve

This site says

User-defined variables names must be preceded by a single at character (@)

That’s what I usually do but recently I was rushing, forgot the ‘@ and wrote the following function which seems to work fine without the variables having ‘@’ at the front.

So is having a ‘@’ in front of a user defined variable a firm requirement or not?

If it is, why does my function work correctly without it?

CREATE  FUNCTION get_next_redacted_member_id() RETURNS INT(11)
       DECLARE result INT SIGNED;
       DECLARE lastid INT;
       INSERT INTO redacted_member_id ( date_used) VALUES ( NOW() ); 
       SET lastid = (SELECT LAST_INSERT_ID() );
       SET result =  -1 * lastid ;
       RETURN result;