I hate to burst your bubble, but you can't actually install modules on perl 4, because they weren't invented until 5.000. You have neither lexical variables, nor references nor use. All you have is local and require. I'm not even sure if :: is used as a package delimiter, I think ' (apostrophe) is the only game in town.

Mind you, what is really fascinating, if you can lay your hands on an old quick reference to perl 4, is just how much there was back then. For a long time I would stumble across nifty tricks and idioms for doing things, thinking it was due to recent patchery and magic, and then when you look at the documentation you see that it was available in the language way back when.

print@_{sort keys %_},$/if%_=split//,'= & *a?b:e\f/h^h!j+n,o@o;r$s-t%t#u'