Camel III does indeed have it, but it doesn't say why the camel was chosen:

"The animal on the cover of Programming Perl, Third Edition is a dromedary (one-hump camel). Camels are large ruminant mammals, weighing between 1,000 and 1,600 pounds and standing six to seven feet tall at the shoulders. They are well known for their use as draft and saddle animals in the desert regions, especially of Africa and Asia. Camels can go for days without water. If food is scarce, they will eat anything, even their owner's tent. Camels live up to 50 years."

The explanation in the text (p. 4) is the following (look up "camel" in the index... Now I have to find out about "bloody camels" and "pink vs. blue camels"!)

"We often joke that a camel is a horse designed by a committee, but if you think about it, the camel is self-sufficient. (On the other hand, the camel has not evolved to smell good. Neither has Perl.) This is one of the many strange reasons we picked the camel to be Perl's mascot, but it doesn't have much to do with linguistics."