Hacker News Reader

This is a totally correct usage, it just makes you sound like a romantic poet or a 19th century orator.

> I believed for a long time that 'else' was just a shorter alternative for 'otherwise'.

It has other uses, but it is that (that is, “or else” is exactly that, and, among other uses, “else” by itself is an accepted short form of “or else”.)

That's valid, if slightly odd, English. More commonly it would be "or else I'll have the OJ".