Replaces occurences of one text string with another.
Syntax:
SUBSTITUTE(text, old:text, new:text {, instance:number})
Replaces occurences of the old text string with the given new text string in the text string.
If instance is omitted, all occurences of the old text string are subtituted.
If instance is supplied, only that particular instance of the old text string is subtituted.
Added in 1.36.