Actually its perl that complains here.

That's what I meant to say ;^) Normally when I'm writing new code at some point I end up wanting to Dumper something, and so recently I've just started adding that automatically to the top of the file. My new mantra is use strict; use warnings; use Data::Dumper, and then after development I'll remove the latter.

I'm glad you posted this because when I read # we have large cyclic structures: disable pretty indent, enable purity mode I realized that my normal use of Dumper in the application I'm writing has been unnecessarily difficult to read. I've got a data structure where trees hang off of digraph nodes and a dump of any element fills the entire screen from side to side -- your version is much easier on the eyes, thanks!