This is a simple example function to show the structure of Lua modules on Mediawiki. Module:Bananas is another version of a "Hello, World!" program.
local p = {}; --All lua modules on Wikipedia must begin by defining a variable
--that will hold their externally accessible functions.
--Such variables can have whatever name you want and may
--also contain various data as well as functions.
p.hello = function( frame ) --Add a function to "my_object".
--Such functions are callable in Wikipedia
--via the #invoke command.
--"frame" will contain the data that Wikipedia
--sends this function when it runs.
local str = "Hello World!" --Declare a local variable and set it equal to
--"Hello World!".
return str --This tells us to quit this function and send the information in
--"str" back to Wikipedia.
end -- end of the function "hello"
return p --All modules end by returning the variable containing its
--functions to Wikipedia.
-- Now we can use this module by calling {{#invoke: HelloWorld | hello }}.
-- Note that the first part of the invoke is the name of the Module's wikipage,
-- and the second part is the name of one of the functions attached to the
-- variable that you returned.
-- The "print" function is not allowed in Wikipedia. All output is accomplished
-- via strings "returned" to Wikipedia.