In some formats fields are delimited using lengthKind="pattern" with an initiator of "/", and a pattern length that means "anything up to but excluding the next /".
These same formats use "-" as a nil value.
The implementation of LiteralNil currently seems to assume delimited length, and scans until end of data. (Should be renamed LiteralNilDelimitedOrEndOfData).
A LiteralNilPattern primitive needs to be created which works more like StringPatternMatched. This primitive needs to be used when the lengthKind="pattern".