declarative-programming

Make types such as Pollable[A], ... opaque.

Add more examples where this pattern shines from the traditional imperative pattern.

• Come up with your own interesting examples.
• Form validations can be messy, maybe a good example around that.
• You can check your current codebase if you find a messy if-else logic that can be converted to this pattern.
• One example can be for a dynamic form, where while filling a field will determine the

Following from #166, trying to compile module name of the form [A-Z][0-9]* should result in an error.