(FunctionClauseError) no function clause matching in anonymous fn/1

currencies returns an unusual shape - a list of maps, each with exactly one key. I’d typically expect either a map of currency name → some value, or a list of tuples ready for List.keyfind if the order is important.

BUT

I also see that the values in currencies don’t have unique keys ("AUD" appears more than once, for instance). What’s the intent of these separate records? That might suggest a better data structure.