Perl itself has no concept of pixels or screens. All it can do is call on libraries that manage displays or abstractions of displays. Most current operating systems will also not allow direct access to the display anyway - usually a program requests a window, which may be a MS Windows type window with title bar, menu etc, or may take up the whole available screen as a drawable map of pixels.
For many applications it's more useful to have the more abstract notion of a canvas, which usually means an area on which you can place a combination of vector (lines, curves, circles, polygons etc) and possibly bitmap primitives with varying levels op transparency, height (IOW place one primitive on top of another), rotations, scaling, translations and so on and let the canvas deal with rendering all those primitives to the screen/window or to some file format (and some file formats like postscript, pdf and svg can store the primitives directly, which is very useful for printing, since you can get a more or less unlimited resolution out of vector primitives)
And this is all just 2D imaging. 3D rendering libraries can be a lot more complex. :-) See OpenGL.