...which we also included as our second cite, and it was only one year later than the earliest Usenet post. (It was the first version of Vromans' Perl Reference Card.)

Our policy for quoting electronic sources is in flux, but one thing that has been decided is that Usenet sources archived on Google Groups can be quoted if they represent the first example of a sense that's otherwise well-attested in printed sources. There are other electronic texts that can be cited under any circumstances (because we believe their dates to be unquestionably accurate), such as the RFC series.