Mmm, you're right about Color::Scheme... not what I thought at first glance...

( ... time passes ... )

Aha! Try Graphics::ColorObject.

If you have access to any graphic app that has an HSB (aka HSV, HSL) color picker with sliders, you can see the desired effect by moving the H slider. That effect can be reproduced using Graphics::ColorObject to build a converter and holding the Saturation and Brightness values constant while varing the Hue.