Regression.pm is a multivariate linear regression package. That is, it estimates the c coefficients for a line-fit of the type y= c(0)*x(0) + c(1)*x1 + c(2)*x2 + ... + c(k)*xk given a data set of N observations, each with k independent x variables and one y variable. Naturally, N must be greater than k---and preferably considerably greater. Any reasonable undergraduate statistics book will explain what a regression is. Most of the time, the user will provide a constant ('1') as x(0) for each observation in order to allow the regression package to fit an intercept. WWW: http://search.cpan.org/dist/Statistics-Regression/