in reply to
What is the best way to dump data structures to logfiles?
I think Data::Dumper is fine for every day purposes. It's pretty fast. My guess is the object oriented interface would make things more log friendly. Also $Data::Dumper::Indent=0 to keep it all on one line.
You might also look at JSON, which may have a way to do single line things, and if that (staying on one line I mean) isn't a concern you might even look at YAML::Syck. It's supposed to be pretty fast, since it uses a c library for ... something.