Here is my brief explanation of the example given on the website in order to clear up some confusion, that I gleaned from the thesis paper. Admittedly, this language does require knowledge of Haskell to really comprehend:

   -- Extract all twin primes from the infinite list of prime numbers with pattern matching!
   def twinPrimes :=
      matchAll primes as list integer with
         | _ ++ $p :: #(p + 2) :: _ -> (p, p + 2)

"matchAll is composed of an expression called target, matcher, and match clause, which consists of a pattern and body expression."

In the example `primes` is a list of primes as in Haskell: `[2,3,5,7...]` considered the "target", and the "matcher" `list integer` may be thought of as a Haskell type like `[Int]`. So I suppose you could simply write it as `primes :: [Int]` and mean the same thing. This notion of a "Haskell list" is important because in the "match clause" the "pattern" is a combination of concatenation using the operator `++` and cons from Lisp using the operator `::`---note that this deviates from Haskell syntax in a somewhat confusing way where Haskell uses `:` and `::` for typing. Nonetheless, the integer list is deconstructed according to concatenation first, in every way, i.e. `[] ++ [2,3,..]`, `[2]++[3,5..]`, etc.., then according to cons'ing with the head stored in the variable `$p`. Yet, the "rest" of the list in this case is actually matched according to the pattern `x::y::_`, therefore, the second element must be 2 from the first, which is why the first pattern `[]++(2::3::_)` is discarded. The `#p` notation simply means to reuse the previous value of p to create a literal match, therefore for the first pattern `p is 2` and `#(p + 2) is 4` thus the pattern becomes 2 followed by 4 followed by the rest, which again doesn't exist. Finally if a match does exist, the values are constructed according to the "body expression", in this case a pair, and all of the results kept in a list. Therefore the type of this value is

   twinPrimes :: [(Int, Int)]