string.trimToLast(stopper) scans astring from the right for stopper, which can be a string or a single character. If found, it removes everything from the beginning upto and including the rightmost occurance of stopper and returns the rest. If stopper is not found, astring itself returned. astring is not modified.
"hello merry world".trimToLast(' ') == "world"
"one::two::three".trimToLast("::") == "three"