You have a precedence problem in your dereferencing ($$_[2] and @$_[1]), i.e. you need additional braces.  And, as moritz said, you need to dereference in the assignment, too. IOW, this should work:

    ...
    print "count is: ${$_[2]} , reference is: $_[2] \n";
    print "data  is: @{$_[1]} , reference is: $_[1] \n";
    ${$_[2]} = 0;
    @{$_[1]} = ();
    ...
[download]