Compiling Spark::List fails due to Global Symbol

[kentfredric]

Global symbol "$list" requires explicit package name at lib/Spark/List.pm line 34.
Global symbol "$list" requires explicit package name at lib/Spark/List.pm line 39.

https://github.com/perl-spark/Spark/blob/master/lib/Spark/List.pm#L28

sub tree_grep {
    my ($self, $subref) = @_;

    for my $i ($list->elements) {
        if ($subref->($i)) {
            return ($i,$self)
        }
    }
    for my $i ($list->elements) {
        if ($i->meta->does('Spark::Role::Container')) {

        }
    }
}