Adding all tracks, I guess

prolog/hello-world/README.md

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+# Hello World
+
+The classical introductory exercise. Just say "Hello, World!".
+
+["Hello, World!"](http://en.wikipedia.org/wiki/%22Hello,_world!%22_program) is
+the traditional first program for beginning programming in a new language
+or environment.
+
+The objectives are simple:
+
+- Write a function that returns the string "Hello World!".
+- Run the test suite and make sure that it succeeds.
+- Submit your solution and check it at the website.
+
+If everything goes well, you will be ready to fetch your first real exercise.
+## Source
+
+This is an exercise to introduce users to using Exercism [http://en.wikipedia.org/wiki/%22Hello,_world!%22_program](http://en.wikipedia.org/wiki/%22Hello,_world!%22_program)
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.

prolog/hello-world/hello_world.pl

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+% Please visit http://exercism.io/languages/prolog/installation
+% for instructions on setting up prolog.
+% Visit http://exercism.io/languages/prolog/tests
+% for help running the tests for prolog exercises.
+
+% Replace the goal below with
+% your implementation.
+
+hello_world(false).

prolog/hello-world/hello_world_tests.plt

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+% Please visit http://exercism.io/languages/prolog/installation
+% for instructions on setting up prolog.
+% Visit http://exercism.io/languages/prolog/tests
+% for help running the tests for prolog exercises.
+
+% The goal below allows tests to be skipped
+% unless the "--all" flag is passed at
+% the command line.
+
+pending :-
+    current_prolog_flag(argv, ['--all'|_]).
+pending :-
+    write('\nA TEST IS PENDING!\n'),
+    fail.
+
+:- begin_tests(hello_world).
+
+    test(hello_world, condition(true)) :-
+        hello_world('Hello World!').
+
+    % Once the first test passes, un-skip the following test by
+    % changing `pending` in `condition(pending)` to `true`.
+    % Repeat for each test until they are all passing.
+
+    test(hello_world_with_a_name, condition(pending)) :-
+        hello_world('Alice', 'Hello Alice!').
+
+    test(hello_world_another_name, condition(pending)) :-
+        hello_world('Bob', 'Hello Bob!').
+
+:- end_tests(hello_world).