Mark Jason Dominus has been programming in Perl professionally since 1992, when he was a UNIX sysadmin with the University of Pennsylvania Department of Computer and Information Sciences. Mark is an occasional contributor to the Perl Core, and is the author of the standard perlreftut man page as well as the Tie::File, Text::Template, and Memoize modules. From 1999-2001, Mark was the managing editor of the www.perl.com website. He was also a columnist for The Perl Journal for several years. All of his articles for TPJ have been reprinted in Computer Science and Perl Programming: Best of the Perl Journal, from O’Reilly and Associates. Mark’s other Perl-related articles have appeared in magazines such as Wiredand IEEE Software. Since 1998, Mark has been a professional Perl trainer. In addition to speaking at conferences such as YAPC, the O’Reilly Open Source Conferences, Usenix, and LISA, he has given training courses for large companies and organizations, including Morgan Stanley, IBM, Bristol-Myers Squibb, and the U.S. Air Force. Mark’s work on Rx, a Perl regular expression debugger, won the 2001 Larry Wall Award for Practical Utility.