Oh it gets better. I don't think anyone in that node
mentioned the following interesting behaviour:
$_ = "Where did I come from?\n";
Isn't that odd? Try this the other way.
$_ = "Bye, bye";
What is going on here? Quite simple. There is a small
list of "special" symbols which are always in package
main by default no matter what package you are in. *_
is one. *INC is another.
But what this really means is that you really share $_
with anything you call, making it easy to have a bad module
wipe out $_ unexpectedly.