use Curses;
That's for a start.
Next, realise that ncurses (the normal curses library on most modern systems) does not automagically paint the whole background of a terminal. It only paints the background where it's told to explicitly draw.
Essentially, if you want a full-screen background, you need to paint over the entire screen with the desired colour, then overlay your other text/colours on top of that.
You may also be able to use panels. Panel support is quite often disabled by default, so it may require a recompile of ncurses -and- then a recompile of the perl Curses module with panels disabled.
