match

    macro
    boot.janet on line 1733, 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 
    are:

    * symbol -- a pattern that is a symbol will match anything, binding 
      `x`'s value to that symbol.

    * array or bracket tuple -- an array or bracket tuple will match 
      only if all of its elements match the corresponding elements in 
      `x`. Use `& rest` at the end of an array or bracketed tuple to 
      bind all remaining values to `rest`.

    * 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.

    While a symbol pattern will ordinarily match any value, the pattern 
    `(@ <sym>)`, where <sym> is any symbol, will attempt to match `x` 
    against a value already bound to `<sym>`, rather than matching and 
    rebinding it.

    Any other value pattern will only match if it is equal to `x`. 
    Quoting a pattern with `'` will also treat the value as a literal 
    value to match against.