condition expression

The condition expression allows one to execute the first piece of code for which the corresponding condition is true. It has the following syntax:

condition
  when X > 0 do
    "positive";
  end

  when X < 0 do
    "negative";
  end

  otherwise do
    "zero"
  end
end

Do blocks may be alternatively written in the arrow form, which accepts a single complex expression:

condition
  when X > 0 => "positive";
  when X < 0 => "negative";
  otherwise => "zero";
end

The otherwise fallback always succeeds (it’s equivalent to when true), and must come at the end of list of conditions.