Yeah I'd expect 20yo Perl5 stuff to work without issues.

A few weeks ago I was experimenting with a sound generation dsl/runtime called Csound and even most 30yo sources were working as long as they didn't use some obsolete UI.

It’s the same with R. The only thing preventing many ancient packages from running under new versions of R and vice-versa is the fact that the package author simply set the minimum version to whatever they happened to be using at the time.