boot.janet on line 1580, column 1
(match x & cases)
Pattern matching. Match an expression `x` against any number of
cases. Each case is a pattern to match against, followed by an
expression to evaluate to if that case is matched. Legal patterns
* symbol -- a pattern that is a symbol will match anything, binding
`x`'s value to that symbol.
* array -- an array will match only if all of its elements match the
corresponding elements in `x`.
* table or struct -- a table or struct will match if all values match
with the corresponding values in `x`.
* tuple -- a tuple pattern will match if its first element matches,
and the following elements are treated as predicates and are true.
* `_` symbol -- the last special case is the `_` symbol, which is a
wildcard that will match any value without creating a binding.
Any other value pattern will only match if it is equal to `x`.