First, let us put this in a slightly more readable format.

@q = qw(hacker. Perl another Just);
sub q { pop @q }

for (0..6) {
        $q = $_ % 2 == 0 ?
            q(&) :
            q(;)
        ;
        print eval "${q}q( )"
}
[download]

Good. That clarifies something. The funny thing here is that q() of course is to qq() what '' is to "" - that is the power of this obfu.

With that in mind, let's put this thing in a more conventional way.

for (0..6) {
        $q = $_ % 2 == 0 ?
            '&' :
            ';'
        ;
        print eval "${q}q( )"
}
[download]

Aha! That exlains a whole lot more! The for loop keeps track of a variable $q that alternates between '&' and ';'. So the string evalled alternates between &q( ) and ;q( ).

By now, the secret is unraveled: the first eval calls the home-made sub, which returns one of the words of a JAPH. The second eval just means ;' ' and returns a space.