There are two string operators. The first is the
    concatenation operator ('.'), which returns the concatenation of its
    right and left arguments. The second is the concatenating assignment
    operator ('.='), which appends the argument on the right side to
    the argument on the left side. Please read Assignment
    Operators for more information.
   
    
   
    See also the manual sections on the 
    String type and 
    String functions.