Fixed occurrence of optional OTHER chars after opening `case` tag.
Added support for `?` after a hash-lookup.
Added support for `term OR term Or term...` in `when` tag.
Added support for `term, term, ...` (commas) in `when` tag.
Added extra `case` unit tests.
Added some comments explaining the algorithm.
Added extra `assign` unit tests.
Added extra `comment` unit tests.
Added extra tag unit tests.
Added extra `case` unit tests.
Added extra lookup unit tests.
Added extra == (equals) unit tests.
Added extra `cycle` unit tests.
Added extra `capture` unit tests.
Added extra `assign` unit tests.
Added extra `unless` unit tests.
Both `nil` and `null` are recognised by the lexer.
Added support for the `empty` function.
Added more statements unit tests.