"next" error

Code.raku

class	DataFlow::Node {}

my @a = ('Hi', 'world');

		my $prev = Nil;
		my @dfns = @a.map: { 
			my $dfn = DataFlow::Node.new();

			$prev == Nil and next $dfn; # Don't link nodes on the ends

			NEXT { $prev = $dfn }
			
			$dfn;
		};

Errors.txt

$ docker exec raku raku test-pass.raku
Use of uninitialized value of type Any in numeric context
  in block  at test-pass.raku line 9
Use of Nil in numeric context
  in block  at test-pass.raku line 9
Cannot resolve caller next(DataFlow::Node:D); none of these signatures matches:
    ( --> Nil)
    (Label:D $x --> Nil)
  in block <unit> at test-pass.raku line 9