I've wanted to do this for a long time, and it's finally happening. I'm using Perl Data Langauge's Levenberg-Marquardt module and it's plotting capabilities to create my very first CPAN module, a module for analyzing spectroscopic ellipsometry data to determine film thicknesss and optical constants. I just added a PDL demo of it in action that you will find when you run 'demo' from within the PDL REPL.