I just read the documentation for ::= , accessed by ? ::=.
1. There is a typo, is -> its.
2. Here as elsewhere, I think that the text for commands should
generally be terminated by $, not ;,
except where the output conveys some information. When it just echos
the input line as in the explanation for macros, it wastes considerable
screen space as well as the time of the reader, who may feel obligated
to study the
output to see what has been transformed, only to find that it is
identical except for
spacing.
3. It would be nice if the documentation were signed.