Source : Free On-Line Dictionary of Computing

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)