For starters, not only are neither standard, one of then never comes with Windows.

There's no generic registration mechanism for locating applications. It doesn't make much sense. It presumes there will only be only one installation of one version of an application on the machine.

I don't know why you'd want to know that information anyway. If you want to load a document, use the user's preferred application:

system(qq{start "" "$doc"});
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