I suspect that the Camel logo came about through a combination of the O'Reilly book designer and Larry Wall's sense of whimsy ("Camel -- a horse designed by a committee" -- old joke). At any rate, the Camel appears on the cover of my first edition of 'Programming Perl' (signed by the authors; it's going to be a collector's item an another thirty years or so....). It would appear that Camels and Perl have been associated together since 1991.