The Jargon File (version 4.4.7, 29 Dec 2003):

one-liner wars
 n.

    A game popular among hackers who code in the language APL (see write-only
    language and line noise). The objective is to see who can code the most
    interesting and/or useful routine in one line of operators chosen from
    APL's exceedingly hairy primitive set. A similar amusement was practiced
    among TECO hackers and is now popular among Perl aficionados.

    Ken Iverson, the inventor of APL, has been credited with a one-liner that,
    given a number N, produces a list of the prime numbers from 1 to N
    inclusive. It looks like this:

            (2=0+.=T?.|T)/T??N

    Here's a Perl program that prints primes:

            perl -wle '(1 x $_) !~ /^(11+)\1+$/ && print while ++ $_'

    In the Perl world this game is sometimes called Perl Golf because the
    player with the fewest (key)strokes wins.


The Free On-line Dictionary of Computing (30 December 2018):

one-liner wars

    A game popular among hackers who code
   in the language APL (see write-only language and line
   noise).  The objective is to see who can code the most
   interesting and/or useful routine in one line of operators
   chosen from APL's exceedingly hairy primitive set.  A
   similar amusement was practiced among TECO hackers and is
   now popular among Perl aficionados.

   Ken Iverson, the inventor of APL, has been credited with a
   one-liner that, given a number N, produces a list of the prime
   numbers from 1 to N inclusive.  It looks like this:

     (2 = 0 +.= T o.| T) / T <- iN

   where "o" is the APL null character, the assignment arrow is a
   single character, and "i" represents the APL iota.

   [Jargon File]

   (2000-03-19)