String expressions consist of combinations of string literals, string variables, string manipulation operators, and parentheses.
Characters that cannot be placed in string literals can be
placed in string expressions using the
operator. Any ASCII character from 0 to 255 is permitted.
The value of a string expression cannot exceed 5120 characters in length. It can be of zero length.
improb SETS "literal":CC:(strvar2:LEFT:4) ; sets the variable
improbto the value "literal" ; with the left-most four characters of the ; contents of string variable