Add rough update of list comprehensions

Author: trosel

doc/Language/haskell-to-p6.pod6

@@ -367,7 +367,41 @@ data shapes become quite intuitive, but it takes a bit of practice.
 
 =head2 List Comprehensions
 
-TODO compare haskell list comprehensions to Perl 6 gather/take
+There are no explicit list comprehensions in Perl6. But rather, you can achieve list comprehensions
+a couple of different ways.
+
+Here is a trivial example in Haskell:
+
+    =begin code :skip-test
+    evens = [ x | x <- [0..100], even x ]
+    =end code
+    
+And now in Perl6 using `if` and `for`:
+
+    =begin code
+    my @evens = ($_ if $_ %% 2 for ^100);
+    =end code
+    
+Here is the creation of tuples in Haskell:
+    
+    =begin code :skip-test
+    tuples = [(i,j) | i <- [1,2],
+                      j <- [1..4] ]
+    -- [(1,1),(1,2),(1,3),(1,4),(2,1),(2,2),(2,3),(2,4)]
+    =end code
+    
+And in Perl6:
+
+    =begin code
+    my @tuples = (1,2) X 1..4;
+    # [(1 1) (1 2) (1 3) (1 4) (2 1) (2 2) (2 3) (2 4)]
+    =end code
+    
+See this design document for more information on what kinds of list comprehensions are possible
+in Perl6: http://design.perl6.org/S04.html#The_do-once_loop
+    
+As you can see, when you get into some more advanced Haskell list comprehensions, Perl6
+does not translate exactly the same, but it's possible to do the same things, nonetheless.
 
 =head2 Fold