Instr(
    ---------------------
    Different to basic
     
     
    Use: Find sub string position.
     
    Syntax is: Instr(string,sub string,start pos)
     
    Example:
     
    Instr("ABC","C",0) = 3
    Instr("ABC","X",0) = 0
    Instr("ABCABC","A",3) = 4
     
    Note: Unlike BBC BASIC, the third parameter is compulsory.
    Note also that the start position is interpreted slightly differently
    from BBC BASIC. To search from the start of a string, use 0,
    not 1 as the start position.