Our look is the result of reader comments, our own experimentation, and feedback from distribution channels. Distinctive covers complement our distinctive approach to technical topics, breathing personality and life into potentially dry subjects. The bird on the cover of Learning Perl/Tk is a juvenile emu (Dromaius novaehollandiae). This large, flightless bird is found throughout the Australian bush steppes. The emu is one of the largest birds in existence, second only to its cousin the ostrich. Adult emus stand about 5 feet (1.5 m) high and weigh up to 120 pounds (55 kg). The grayish brown emu's small wings contain ony six or seven feathers. They are hidden by the long, hairlike rump plumage. Emus have extremely strong legs, which they use as defensive and offensive weapons when fighting. A human limb can be broken by a kick from an emu. Their powerful legs makes emus strong swimmers and fast runners, reaching speeds of up to 50 km/hour.

Male emus, who are slightly smaller than the females, tend to the incubation of eggs and the raising of the young. An emu nest contains up to 15-25 deep green eggs, laid by several hens. Incubation of the eggs takes from 25 to 60 days. The large discrepancy in incubation time is because the male needs to leave the nest periodically to find food and drink. How long he is away affects the time for incubation. Newly hatched emus weigh about 15 pounds (440 g). They are grown at two to three years.

The relationship between emus and Australian farmers has always been an adversarial one; three coastal subspecies of emu have been exterminated. Because emus can jump over high fences, it is diffucult to keep them out of fields, where they eat and trample crops. In the arid Australian bush, emus also compete with cattle and sheep for grass and water. On the other hand, emus eat many insects that would otherwise eat the crops. In 1932 Australian farmers declared war on the emus, making an all-out effort to eradicate them. Fortunately, the effort failed. The battle between emus and farmers continues to this day. Edie Freedman designed the cover of this book, using a 19th-century engraving from the Dover Pictorial Archive. The cover layout was produced with Quark XPress 3.3 using the ITC Garamond font.

The inside layout was designed by Edie Freedman and implemented in gtroff by Lenny Muellner. The text and heading fonts are ITC Garamond Light and Garamond Book. The illustrations that appear in the book were created in Macromedia Freehand 7.0 by Robert Romano. This colophon was written by Clairemarie Fisher O'Leary.