sql_mode = Oracle with MariaDB 10.3.4 and Store procedure

create or replace function ean_13(P_Str In Varchar2) Return Varchar2 Is 

l_Sum Number; 

l_Multiple Number; 

Begin For I in 1..12 Loop

 If mod(i,2) = 0 Then

 l_Multiple := 3;

 Else l_Multiple := 1;

 End If;

 l_Sum := Nvl(l_Sum, 0) + Substr(P_Str, i, 1) * l_Multiple; End Loop; 

If Floor(l_Sum/10) - Mod(l_Sum, 10) = Substr(P_Str, 13) Then Return('TRUE');

Else Return('FALSE'); 

End If; 

End; /