use v6;

class Point {
    has $.x = 0;
    has $.y = 0;

    method gist { "[$.x, $.y]" }

    method set( :$joe = $!x, :$susan = $!y ) { 
        $!x = $joe; 
        $!y = $susan;
    }
}

my $point = Point.new();
say $point.x;   # 0
say $point;    # [0, 0]
# $point.x = 3;  Error!

$point = Point.new(x => 3, y => 5);
say $point;  # [3,5]

$point.set(joe => 10, susan => 20);
say $point;  # [10, 20]

$point.set(joe => 100);
say $point;  # [100, 20]