Evil reuse of `$` variable.

For those of you who believe that a variable should only serve one
purpose, maybe even have a meaningful name, I'd probably agree that this
particular reuse is abusive. `$` has a special meaning to me and the use
to count the arity of the function offends my sensibilities too.

But, 2 bytes is 2 bytes.

See #46.

File                             Raw         Min         Zip     Min/Zip
index.js                  5665/05.53  2118/02.07  1890/01.85  1009/00.99