Then what's a "try"? I'm also confused by this. How are eggs not tries?

No details about what to implement. Even just some tests to show how it should behave would be useful. At first it appears as though it should just concatenate strings.

Your tests seem to be trying to call your _rest function on the integer 1. It calls _first on the initial array and then _rest on 1, resulting in a TypeError: Object 1 has no method 'slice'.

EDIT: My mistake. I had mistaken the specification for compose to take the functions in the same order as pipeline. I was doing compose backwards.