Man pages matching name statistics::basic::leastsquarefit in section 3pm:

Statistics::Basic::LeastSquareFit.3pm.en	debian 10 / libstatistics-basic-perl
Statistics::Basic::LeastSquareFit.3pm.en	debian 11 / libstatistics-basic-perl
Statistics::Basic::LeastSquareFit.3pm.en	debian 12 / libstatistics-basic-perl