Wakaba Spoiler tags

Hey guys, I'm trying to add spoiler text support to wakaba, and I'm new to perl so this is a lot harder for me than it should be. Is there any reason why adding the following to sub do_wakabamark($;$$) is not working?

elsif(/^\[spoiler\]/) # spoilers{
    if ($lines[0]=~/^\[spoiler\](.*)/){
        while !($lines[0]=~/\[\/spoiler\]$/){
            push @spoiler,$1; shift @lines;
        }
    }
    $res.="<span class='spoiler'>".(join "<br />",@spoiler)."</span>";
}
Thanks in advance!!