And what is a 3-D rectangle? Do you mean a bidimensional representation of an otherwise solid object (like an isometric or perspective drawing of a prism), or a rectangle (which is a 2-dimensional, flat object) drawn "skewed" to appear as if it's "rotated around some appropriate axis"?

Anyway, Perl/Tk has a great widget for drawing, Tk::Canvas. For 2-D drawing, that is.

If you really need simulated 3-d, I'd suggest you use OpenGL.

-- 
        dakkar - Mobilis in mobile

"3D rectangle" is kind of vague. If he used terminologies like cube, tetrahedron, dodecahedron etc, I would be 100% percent sure about what he meant, but "3d rectangle"...

There is a chance that he might actually mean a rectangle with certain relief, and 3D alike, for example, a Tk button created like this:

$mw->Button(relief => "sunken");
[download]

is 3D alike.

If this is what he meant, what he really want is simply 2D shapes with "shadows". If this is the case, then much less maths is needed, and more importantly one needs a sharp sense of colors.

use strict;
use VRML;

my $vrml = new VRML(2);
$vrml->Group->Shape(
    sub{$vrml->IndexedFaceSet(
        sub{$vrml->Coordinate('0 0 0', '0 0 1', '0 1 0', '0 1 1', '1 0
+ 0', '1 0 1', '1 1 0', '1 1 1', )->insert('solid FALSE')}, 
        ['0 1 3 2', '0 1 5 4', '0 4 6 2', '4 5 7 6', '2 3 7 6', '1 3 7
+ 5']
    )},
    sub{$vrml->Appearance(
        sub{$vrml->Material(
            ambientIntensity => .5, 
            diffuseColor => '1 0 0',
            emissiveColor => '.25 0 0'
        )}
    )}
)->back;
$vrml->print;
$vrml->save;
exec 'vrmlview /home/phil/usr/vrml_test.wrl'; #Substitute your own vie
+wer and path info here.
[download]

Aside from allowing you to see complex shapes that are hard to visualize otherwise, the effects of grabbing an object with your mouse and rotating it in multiple axes can be downright intoxicating! Try it because it's fun, if for no other reason!

For an approach that uses Z-buffering to draw shapes in 3-space, see this node. It isn't fast, though.