Math::Interval seems to be a good fit. It clearly describes the namespace of this mathematical niche, ala Math::Combinatorics.
I had been wondering if it might be prudent to use something like Math::Interval::Arithmetic for what you are currently proposing, just in case someone (possibly you) wants to write Math::Interval::Calculus in the future but if combinatorics can fit into one module then I'd imagine that interval analysis probably can too.