> The user can either pick ..1 and be incompatible with R6RS, or pick __1
> and be incompatible with other WCS implementations.  It will probably be
> easier to fix other WCS implementations than R6RS.

Since `...` and `..1` and `..=` are analogous to the regexp matchers
`*`, `+` and `=` would it work to use those one-character identifiers?
Those have got to be permitted in all Scheme implementations since they
are needed for standard number procedures.

In SRFI 204 there's one more:

..* k j   between k and j matches, where k and j are integers.

But that seems like a new invention in the SRFI? It's not in the Chibi
match manual at
<http://snow-fort.org/s/gmail.com/alexshinn/chibi/match/0.9.0/index.html>.

The identifier `...` is nice since it's already used in syntax-rules,
but if `...` is not portable it could have `*` as an alias.