Unique identification for an object
class ObjAt is Any {}
Objects of type ObjAt are the return value of .WHICH calls on other objects, and identify an object uniquely.
If two objects compare equally via ===, their .WHICH methods return the same ObjAt object.
See also ValueObjAt for value types.
multi infix:<eqv>(ObjAt:D $a, ObjAt:D $b)
Returns True if the two ObjAt are the same, that is, if the object they identify is the same.
my @foo = [2,3,1];
my @bar := @foo;
say @foo.WHICH eqv @bar.WHICH; # OUTPUT: «True»