Mostly the compiler deals in terms of PackageNames, which don't have the version suffix. This is so that we don't need to know the version for the -package-name flag, or know the versions of wired-in packages like base & rts. Versions are confined to the package sub-system.

This means that in theory you could have multiple base packages installed (for example), and switch between them using -package/-hide-package.

A PackageId is a string of the form pkg>-<version.