Attempt to match a value against several patterns.

Each clause must be a pattern, followed by zero or more forms. The match macro evaluates val, then attempts to match it against each pattern in turn, evaluating and returning the body of the first clause which matches.

If none of the patterns match, the match form returns #n.

(match arg
  (i : int?
    "the integer {i}")
  ((a : int?, b : int?)
    "a pair of integers, ({a} {b})")
  (_ : obj?
    "an object")
  (arg
    (bail "unexpected argument {arg}")))