For your task PDL will be enormously valuable. It will be worth every bit of effort to obtain and learn it.

There is the nice PDL::Fit::Linfit module which does a general curve-fit to a linear combination of specified functions.

PDL also has functions for selecting the inconsistent data, creating plots, and generating statistical summaries.

The PDL module is a perl extension written in C and FORTRAN. In my experience it is many times faster than the equivalent routines written in pure perl. It should be quick with 40,000 point datasets.

It should work perfectly the first time! - toma