Comment lines and blank lines are ignored. The line may start with white-space. The second number must be greater or equal to the first number. There can be optional text after the two numbers to annotate the line. White-space before or after the text is removed.
Data files None.
Warnings You can mask out a complete sequence. It exits with status 0, unless a region is badly constructed. Known bugs None. This program is intended to be used by everyone and everything, from naive users to embedded scripts.