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The animals on the cover of Mastering Perl are a vicuña (Vicugna vicugna) mother and her young. Vicuñas are found in the central Andes Mountains of South America, at altitudes of 4,000 to 5,500 meters. For centuries, the vicuña has been treasured for its coat of soft, insulating hair that produces some of the finest and rarest wool on Earth. Vicuña yarns and fabrics can fetch up to $3,000 per yard.

Vicuñas held a special place among ancient Incan societies. Incans believed that the animal was the reincarnation of a beautiful maiden who had received a coat of gold as a reward for succumbing to the advances of a decrepit and homely king. Every four years, Incans would hold a chacu, a hunt to trap thousands of vicuñas, shear their coats, and release them back to the wild. Incan law forbade the killing of vicuñas, and only members of royalty were allowed to wear garments made from the animal's coat.

Unregulated hunting of vicuñas led to the animal being placed on the endangered species list in 1974. By that time, their number had dwindled to 6,000. However, close regulation, particularly by the government of Peru, has led to the vicuña's resurgence, and today the number is over 120,000. The chacu is now sanctioned and regulated by the Peruvian government, and a portion of the profits is returned to villagers in the Andes.

The cover image is a 19th-century engraving from the Dover Pictorial Archive. The cover font is Adobe ITC Garamond. The text font is Linotype Birka; the heading font is Adobe Myriad Condensed; and the code font is LucasFont's TheSans Mono Condensed.