I'm a big fan of Xperl but somethings bugging me and that's the target frame, it's messy. I don't know if I missed the option or the author did but I can't seem to filter the debuffs of the target frame. Basically I only want it to show what's important to my class, I have no need seeing poison stacks, fireballs stacks etc.

Any help would be great.

I believe (Not infront of game now) that there is options to turn off your targets buffs or at least change the size of the buff display.  I believe its in the top right corner of the target options tab.

I can show only castable buffs, but not only castable debuffs, which is the real problem. My target frame is spammed by other peoples debuffs.

I don't remember exactly how I did it but on the target frame my buff/debuffs on the target show in larger scale then the other party members buffs/debuffs. I also believe you can change the scale of them totally.  I know that not exactly what your looking for but maybe it will help you out with the big mess that shows up.

Also maybe requesting a feature on the wowace page will get your request added.  Never know till you try. http://www.wowace.com/projects/xperl/tickets/