strng is a character string (or variable with a value that is a character string). Mandatory.
string1 is a character string (or variable with a value that is a character string) that is to be replaced by string2 in strng. Mandatory.
string2 is a character string (or variable with a value that is a character string) that is to replace string1 in strng. Mandatory.
firstOccur is an Integer value that represents an occurrence, or the beginning of a range of occurrences, of string1 that is to be replaced by string2. Optional. When firstOccur is omitted, the first occurrence of string1 is replaced by string2.
lastOccur, if firstOccur has been specified, can be specified as an integer that represents the last occurrence in a range of occurrences of string1 that is to be replaced by string2. Optional. The default value is the value of argument firstOccur.
