Of late I've been picking up some design insights from a different perspective, by reading Doing Hard Time: Developing Real-Time Systems with UML, Objects, Frameworks and Patterns, by Bruce Powel Douglass.

Much of my professional life has been lived with the attitude that "by the time it ships, we'll have twice the memory and twice the processor power, so don't worry about _______," which is fine with many classes of applications, but not for those that have rigid response constraints and Very Bad Consequences for missing them. Learning some of what hardcore embedded designers go through to make reliable, safe systems has been a real eye openner. It might not apply directly to Perl, but good ideas make great compost.