learn perl 3rd ed

Ch1. introduction

(page 18)

Why Are There So Many Footnotes?

Thank you for noticing.

But it means that we can’t honestly say, “The fizzbin operator frobnicates the
hoozistatic variables” without a footnote giving the exceptions.*

Many of the exceptions have to do with portability.

And many of the other exceptions have to do with the old “80/20” rule.