use v5.20;
use experimental 'signatures';

package Point {
	sub new ($class, $x, $y) {
		bless [$x, $y] => $class;
	}
	sub x ($self) { $self->[0] }
	sub y ($self) { $self->[1] }
	sub inverted ($self) {
		ref($self)->new($self->y, $self->x);
	}
}

##</code><code>##

my Foo $foo = Foo->new(...);

##</code><code>##

sub foo (Int $bar, Str $baz) {
   ...;
}

##</code><code>##

sub foo {
   my Int $bar = $_[0];
   my Str $baz = $_[1];
   die "..." if @_ > 2;
   ...;
}

##</code><code>##

my Foo $x = $y;

##</code><code>##

"Foo"->CHECK_SCALAR(\$newvalue);
Foo()->CHECK_SCALAR(\$newvalue);

##</code><code>##

sub UNIVERSAL::CHECK_SCALAR (Str $class, ScalarRef $sref) {
   require Scalar::Util;
   unless (Scalar::Util::blessed($$sref) && ${$sref}->isa($class)) {
      require Carp;
      Carp::croak("...");
   }
}