What's the first (oldest) language that had the 'Unless' conditional/loop built into itself?

Where an example could be

unless (myVar) == if (!myVar)

until (myVar) == while (!myVar)
  • Is this just in Perl & Ruby? It's not one I've come across before.
    – ChrisF
    Commented Apr 7, 2011 at 12:39
  • I found it in Common Lisp yesterday, and I just had a discussion with a friend that lead to this question. Not sure whether it existed in MACLISP..
    – Zolomon
    Commented Apr 7, 2011 at 12:42
  • 4
    That's an odd interpretation of "unless". I would have defined it as unless (myVar) == if (!myVar) and until (myVar) == while (!myVar). Commented Apr 7, 2011 at 15:09
  • @Adam Paynter: That's what unless and until do in Ruby and Perl. I'm not quite sure which language the OP is talking about. Commented Apr 7, 2011 at 17:08
  • The above example was one interpretation that I had come across - apparently there are varieties!
    – Zolomon
    Commented Apr 8, 2011 at 6:57

4 Answers 4


actually I've found a copy of the 1967 BCPL language manual with the UNLESS statement in it on section 6.7


this was also the first language to demonstrate the "Hello World" program

BCPL became "B" at Bell Labs and then later "C"

the joke was that the real question was what would the next language be "P" from the BCPL or "D" from the Alphabetic order

  • 3
    Great first answer, hope you stick around and write more quality content like this here. Commented Apr 17, 2013 at 17:02

The first language I ever saw with an UNLESS statement was Intercal, whose primary control structure was the COME FROM ... UNLESS ... statement. Intercal wasn't designed as a serious language, but it does date from 1972, and you can program in it (why you'd want to is another matter).


I think it originated with BASIC-PLUS on Digital systems in the '70s.

The Perl documentation mentions this heritage (run perldoc perl and look in the DESCRIPTION)


LISP, invented in 1958, though not sure when LISP got the UNLESS keyword.

Not the answer you're looking for? Browse other questions tagged or ask your own question.