JS closures lose context

[Andy Armstrong]

Given this code:

----------------------------------------------------
#!/usr/bin/perl -w

use strict;

$| = 1;

use JavaScript;
my $rt = JavaScript::Runtime->new();
my $cx = $rt->create_context();

sub get_js {
    my $next = 1;

    # Make a perl function
    $cx->bind_function(perl_next => sub {
        return $next++;
    });

    $cx->eval(q{
        function makeClosure() {
            var next = 1;
            var js_next = function() {
                return 1;
                return next++;
            }

            return function() {
                return perl_next() * js_next();
            }
        }
    });

    return $cx->call('makeClosure');
}

my $clos = get_js();

print "$clos\n";

for (1..10) {
    print $clos->(), "\n";
}

----------------------------------------------------

The call to $clos->() returns undef. If the returned JS function is  
modified to

            return function() {
                return perl_next() * next++;
            }

each call returns nan. If modified to

            return function() {
                return perl_next();
            }

it correctly returns 1..10.

It looks as if the context that should be captured (closed over) by  
the returned JS function is being lost. Is this expected behaviour?

--
Andy Armstrong, hexten.net