Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)

fun String.substringBeforeLast(
    delimiter: Char, 
    missingDelimiterValue: String = this
): String

fun String.substringBeforeLast(
    delimiter: String, 
    missingDelimiterValue: String = this
): String

Returns a substring before the last occurrence of delimiter. If the string does not contain the delimiter, returns missingDelimiterValue which defaults to the original string.