Thomas S. "Tom" Christiansen (born February 13, 1963), nicknamed tchrist or occasionally thoth, is a

Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and ot ...

developer and user known for his work with the

Perl Perl is a family of two high-level, general-purpose, interpreted, dynamic programming languages. "Perl" refers to Perl 5, but from 2000 to 2019 it also referred to its redesigned "sister language", Perl 6, before the latter's name was offici ...

programming language. Christiansen worked for several years at TSR Hobbies before attending the

University of Wisconsin - Madison A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. ''University'' is derived from the Latin phrase ''universitas magistrorum et scholarium'', which rou ...

where he earned

B.A. Bachelor of arts (BA or AB; from the Latin ', ', or ') is a bachelor's degree awarded for an undergraduate program in the arts, or, in some cases, other disciplines. A Bachelor of Arts degree course is generally completed in three or four years ...

's in Spanish and Computer Science, and an

M.S. A Master of Science ( la, Magisterii Scientiae; abbreviated MS, M.S., MSc, M.Sc., SM, S.M., ScM or Sc.M.) is a master's degree in the field of science awarded by universities in many countries or a person holding such a degree. In contrast to ...

in Computer Science. He worked for five years at

Convex Computer Convex Computer Corporation was a company that developed, manufactured and marketed Vector processor, vector minisupercomputers and supercomputers for small-to-medium-sized businesses. Their later Exemplar series of parallel computing machines wer ...

. In 1993, he established the Tom Christiansen Perl Consultancy, located in

Lake Geneva, Wisconsin Lake Geneva is a city in the U.S. state of Wisconsin. Located in Walworth County and situated on Geneva Lake, it is home to an estimated 8,105 people as of 2019, up from 7,651 at the 2010 census. It is located about 40 miles southwest of Milwa ...

. In 2010, he joined the Biomedical Text Mining Group at the University of Colorado School of Medicine. Christiansen, with a C- and-Unix background, was one of the early contributors to Perl after its public release in 1987. He presented the first public Perl tutorial in 1989 and wrote the first academic paper to highlight Perl in 1990. He was the author of much of the core Perl documentation, including the manual pages perlfaq and perltoot, development of ''perl.com''. In 1996, Christiansen wrote "''Csh Programming

Considered Harmful GoTo (goto, GOTO, GO TO or other case combinations, depending on the programming language) is a statement found in many computer programming languages. It performs a one-way transfer of control to another line of code; in contrast a function ca ...

''" about the limitations inherent in

C Shell The C shell (csh or the improved version, tcsh) is a Unix shell created by Bill Joy while he was a graduate student at University of California, Berkeley in the late 1970s. It has been widely distributed, beginning with the 2BSD release of the ...

Programming. Books he co-authored include: *The second (1996) and third (2000) editions of ''

Programming Perl ''Programming Perl'', best known as the Camel Book among programmers, is a book about writing programs using the Perl programming language, revised as several editions (1991-2012) to reflect major language changes since Perl version 4. Editions ...

''. *The second (1997) edition of ''

Learning Perl ''Learning Perl'', also known as the llama book, is a tutorial book for the Perl programming language, and is published by O'Reilly Media. The first edition (1993) was authored solely by Randal L. Schwartz, and covered Perl 4. All subsequent edi ...

'' (and its spin-off ''

Learning Perl on Win32 Systems Learning is the process of acquiring new understanding, knowledge, behaviors, skills, values, attitudes, and preferences. The ability to learn is possessed by humans, animals, and some machines; there is also evidence for some kind of learnin ...

''). *'' The Perl Cookbook'' (1998). In 1999, Christiansen was one of the original recipients of the

White Camel award The "White Camel" award is given to important contributors to the Perl Programming Language community. The awards were initiated by Perl Mongers and O'Reilly & Associates at The Perl Conference in 1999. Today, The Perl Foundation acknowledges ...

s from Perl Mongers for his contribution to Perl's documentation. Christiansen has been called a "UNIX luminary". The common phrase "Only perl can parse Perl" is attributed to Tom Christiansen, although it probably was inspired from "Only tex can understand

TeX Tex may refer to: People and fictional characters * Tex (nickname), a list of people and fictional characters with the nickname * Joe Tex (1933–1982), stage name of American soul singer Joseph Arrington Jr. Entertainment * ''Tex'', the Italian ...

Randal Schwartz Randal L. Schwartz (born November 22, 1961), also known as merlyn, is an American author, system administrator and programming consultant. He has written several books on the Perl programming language, and plays a promotional role within the Per ...

also credits him with accidentally naming the Schwartzian Transform for optimizing some types of sorts. This happened after Schwartz used it in a

Usenet Usenet () is a worldwide distributed discussion system available on computers. It was developed from the general-purpose Unix-to-Unix Copy (UUCP) dial-up network architecture. Tom Truscott and Jim Ellis conceived the idea in 1979, and it was ...

message, and Christiansen replied to the message giving some corrections and in one place said "the Schwartzian transform" to refer to the transform that Schwartz used.

References

External links

* (1999
"Plural of Virus"
* perl.co

* UNIX faq - shel
"Csh Programming Considered Harmful"
* (1991
"GUIs Considered Harmful"

PerlMonks ''PerlMonks'' is a community website covering all aspects of Perl programming and other related topics such as web applications and system administration. It is often referred to by users as 'The Monastery'. The name PerlMonks, and the general sty ...

* (1997
Interview with Tom Christiansen and Larry Wall
Web Review magazine, Feb 28, 1997 issue (link to archived copy) * (2009

{{DEFAULTSORT:Christiansen, Tom 1963 births Living people Perl writers O'Reilly writers University of Wisconsin–Madison College of Letters and Science alumni