I talked to the folks in #chicken (on irc.freenode.net), and the
discussion yielded a clarification:
To represent tail notation like
(define (foo . args))
either avoid a linebreak before the dot as in
define : foo . args
or use a double dot to start the line:
. . args
The first dot mark the line as continuation, the second enters
the scheme code.
Later reflection provided two clarifications to avoid limiting future
uses of the dot as syntax.
A dot as symbol at the end of a line is reserved for potential
future use. It should be a syntax error if the next non-empty line
starts with non-zero indentation. A lone dot at the end of a line
calls for hard to catch errors.
A dot as only symbol in a line has no useful meaning: the line is
by definition empty. As such, a dot as only symbol on a line is
also reserved for future use and should be treated as a syntax
error to avoid locking out future possibilities.
I attached an updated version of the SRFI.
singing a part of the history of free software: