zodiac:match-against

• (zodiac:match-against pattern exp env) -> (union penv #f)
      pattern : zodiac:cpat
      exp : zodiac:read
      env : zodiac:env

  match-against performs the actual matching of a given expression (of type read) against a compiled pattern. If the expression matches the pattern, a pattern environment, which is a non-false value, is returned; else the result is #f.