Thanks for all your effort.

As for the tutorial you mention, it seems that it is not quite complete and some things seem to be just a little bit different on my system.

E.g. I do not need to build make, but I need to install perlbase-dumpvalue to make cpanm work.

But I can use cpanm like this now:

curl -L https://cpanmin.us | perl - -M https://cpan.org -n <module>
[download]

Again I need to use cpan.org and not cpan.metacpan.org as in the tutorial, as otherwise the modules are not found.

But of course when I try this to install Net::SSLeay it fails becuase of the missing EXTERN.h.

I is totally unclear to me how the author of this tutorial who initially also had the problem of a misssing EXTERN.h managed to make this problem go away.

This is magic that I cannot reproduce.