Function becomes case-sensitive on a different server

Question

I have created the below function in mysql:

DELIMITER $$
CREATE FUNCTION fn_header_uploader_address(v_add varchar(500)) RETURNS bigint(20)
begin
DECLARE v_error bigint default 0;

    IF length(v_add) > 100 then
        set v_error = 110;  
    elseif v_add is null or v_add ='' then 
        set v_error=110;
    elseif v_add NOT REGEXP '^[A-Z0-9._%-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$' then
        set v_error=110;
    end if;   
return v_error;

end$$
DELIMITER ;

If I run it on local (deterministic/no deterministic clause) , it returns zero (valid email) for the below statement:

select fn_header_uploader_address('hello@gmail.com');

but on moving the function to a new server, this become case sensitive !! So now

select fn_header_uploader_address('hello@gmail.com'); ---- error 110

Any help please ?

Edit:

I have already compared the servers using the below commands:

show collation where collation like '%_c%' ;
show variables like '%version%';

Answer 1

Change:

...
elseif v_add NOT REGEXP '^[a-zA-Z0-9._%-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}$' then
...

or binary:

...
elseif v_add NOT REGEXP '^[\x41-\x5a\x61-\x7a\x30-\x39\x2e\x2d\x5f\x25]+\x40[\x41-\x5a\x61-\x7a\x30-\x39\x2e\x2d]+\x2e[\x41-\x5a\x61-\x7a]{2,4}$' then
...