Errata: Chapter 3 - page 31, missing `return -1;` after `perror`

**Chapter:** 3
**Description:** In the code snipped of page 31 there is no `return -1;` after the call to `perror`. It seems off considering that in all other places where an error ocurrs it returns -1. Additionally, in page 35 the `return -1;` is there, it seems like it was missed in page 31.
