I'm hearing a lot of good things about Mouse as a lighter-weight alternate to Moose.

Actually, we have been discouraging the use of Mouse since it is just impossible to make Mouse and Moose smoothly interact with one another. Any::Moose was an attempted solution to this, and it works to a degree, but all too often Mouse code will outgrow what Mouse can provide and the author will end up switching to Moose. This is exactly what happened with CHI actually.