Whistle is a web server built on top of Toot
(https://github.com/gigamonkey/toot).

Toot provides the low-level HTTP plumbing and hands off each request
to a handler. Whistle is one such handler that can be configured via
config files (not code) to automatically redirect certain urls
elsewhere; to require basic-authentication for certain urls; and to
handle urls matching specific patterns with specific functions.