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 animal on the cover of Perl 6 Essential is an aoudad (ammotragus lervia). Commonly known as Barbary sheep, aoudads originated in the arid mountainous regions of northern Africa and have stout, sturdy bodies, standing 75-100 centimeters at the shoulder and weighing from 30-145 kilograms. The aoudad has a bristly reddish-brown coat and is distinguished by a heavy, fringed mane covering its chest and legs. Both males and females have thick, triangular-shaped horns that curve back in a semicircle. A male aoudad's horns can grow up to 85 centimeters.

Aoudads are herbivores and are most active at dawn and dusk, avoiding the desert heat of midday. They will drink water if it is available, but can obtain sufficient moisture from dew and vegetation. Aoudads are incredible jumpers, able to clear 6 feet from a standstill. So well suited are they to their surroundings that newborns have the ability to navigate rocky slopes within just hours after birth.

Despite being endangered in their native environment, aoudads are flourishing in the United States. Introduced to western Texas and southern New Mexico in the 1940s, aoudads are now so populous that it is feared that their presence may threaten the native desert bighorn sheep. Aoudads are considered native game in the desert mountains of their adopted home, where the rugged landscape is dotted with ranches catering to recreational hunters. Emily Quill was the production editor, and Sarah Jane Shangraw was the copyeditor for Perl 6 Essentials. Phil Dangler and Mary Anne Weeks Mayo provided quality control. Jamie Peppard provided production assistance. Julie Hawks wrote the index.

Ellie Volckhausen designed the cover of this book, based on a series design by Edie Freedman. The cover image is a 19th-century engraving from Animate Creations, Volume II. Emma Colby produced the cover layout with QuarkXPress 4.1 using Adobe's ITC Garamond font.

David Futato designed the interior layout. This book was converted by Andrew Savikas to FrameMaker 5.5.6 with a format conversion tool created by Erik Ray, Jason McIntosh, Neil Walls, and Mike Sierra that uses Perl and XML technologies. The text font is Linotype Birka; the heading font is Adobe Myriad Condensed; and the code font is LucasFont's TheSans Mono Condensed. The illustrations that appear in the book were produced by Robert Romano and Jessamyn Read using Macromedia FreeHand 9 and Adobe Photoshop 6. This colophon was written by Emily Quill.