// Motivation #1
// Hiding some stuff from accidental access
public region debug;
public region deprecated;

struct IRBuilder {
	...

	// this variable is only relevant for debugging
	// so it is either must be used by a function within the debug region,
	// or the user must explicitly opt-in with the debug:: prefix
	// (or 'use region debug')
	var debug::instr_count: i32 = 0;
}

implementation IRBuilder {

	method create_phi(self: IRBuilder, bracnhes: i32): PHINode {
		...
	}

	// you cannot use a deprecated function unless you are deprecated yourself,
	// or opt in
	method deprecated::create_phi(self: IRBuilder): PHINode {
		...
	}

	method debug::print_next_name(self: IRBuilder) {
		...
	}

	method debug::print_instr_count(self: IRBuilder) {
		...
	}

}


// Motivation #2
// API versioning

public region v1;
public region v2 (v1);
public region v3 (v2);
public region v4 (v3);

// we can use the version tag for function selection:
function v4::connect();
function v3::connect();
function v1::connect();

function client() {
	use region v3;
	connect(); // selects v3::connect, even when v4 or v5 arrives
}

// cannot accidently use a newer version if didn't opted in for it:
function v4::new_stuff_added_in_4();

function i_use_old_one() {
	use region v2;
	new_stuff_added_in_4(); // fail
}


// other useful semantical tagging (unsafe, throws, blocking...)