Well once upon a time there was a flamewar on p5p. It was not a small flamewar. It was one of those things which went on and on and on through hundreds of messages. It was originally about whether chmod should accept symbolic modes (eg "o+w" to add write permission for the owner). Some liked the idea. Others though it was bloat. Some thought that people who couldn't sling bits were better off serving Real Programmers their fries. You know how it is.

As these things will go, it digressed. One of many threads got into some complaining about what beasts the FileHandle and IO::* modules had turned into, with a comment that the actual need was simple.

At that point Tom Christiansen replied pointing out that the original need was already met. There was some discussion and surprise as people wondered how it worked. Not all of which is easy to trace in the link because the thread was so long that the automatic thread reconstruction is a little flaky...

The construct was around before that. I don't know when it was originally discovered, but certainly many big names in the Perl community were surprised by it in 1999.