A reversible_pattern is a pattern that can be matched end-to-start.
interface reversible pattern[contravariant readonly value element type]
extends pattern[element type]
Gets the last non-empty match in the end-to-start direction.
When end_index is specified, it defines the element index after the last element
index after the one being matched. If end_index is null, it defaults to
the_list.size.
range or null find last(readonly list[element type] the list, nonnegative or null end index)