I always use File::Spec for assembling paths (although it isn't a standard practice where I work; I also use File::Temp and File::Copy for added safety and portability, but those modules are outside the scope of the question). Since File::Spec is part of the core distribution I probably wouldn't use a module that creates an extra dependency. Not sure about edge cases, but differences between absolute and relative paths could cause issues if they aren't standardized before comparison.