Man pages matching name image::math::constrain in section 3pm:

Image::Math::Constrain.3pm.en	debian 10 / libimage-math-constrain-perl
Image::Math::Constrain.3pm.en	debian 11 / libimage-math-constrain-perl
Image::Math::Constrain.3pm.en	debian 12 / libimage-math-constrain-perl