Problem Statement

Find the index of a string (needle) in an indexable, ordered collection of strings (haystack). Raise an exception if the needle is missing. If there is more than one occurrence then return the smallest index to the needle. Return the largest index to a needle that has multiple occurrences in the haystack.

Let's start with the solution:

haystack: [Zig Zag Wally Ronald Bush Krusty Charlie Bush Bozo]

loop [Bush Washington] 'needle [
    i: index haystack needle

    if? empty? i    -> panic ~"|needle| is not in haystack"
    else            -> print [i needle]
]