boot.janet on line 1987, column 1
Shorthand for fn. Arguments are given as $n, where n is the
0-indexed argument of the function. $ is also an alias for the
first (index 0) argument. The $& symbol will make the anonymous
function variadic if it apears in the body of the function - it can
be combined with positional arguments.
* (short-fn (+ $ $)) - A function that doubles its arguments.
* (short-fn (string $0 $1)) - accepting multiple args
* |(+ $ $) - use pipe reader macro for terse function literals
* |(+ $&) - variadic functions