It seems that DOM nodes do not necessarily support the .hasOwnProperty method. Until a new version of MozRepl::RemoteObject is released that does not rely on the object itself supporting hasOwnProperty, you will have to use this as a local patch workaround to MozRepl::RemoteObject:

    my $getKeys = $ff->application->repl->declare(<<'JS', 'list');
    function(obj){
        var res = [];
        for (var el in obj) {
            if (Object.hasOwnProperty.apply(obj,[el])) {
                res.push(el);
            };
        }
        return res
    }
JS
[download]

But please do not use weird, undocumented methods to look inside elements. Use normal Perl hash methods:

my @keys = keys %$link;
[download]