In message "[ruby-talk:24736] Negate grep pattern match?"
    on Fri, 9 Nov 2001 13:57:05 +0900,
    Jos Backus <josb / cncdsl.com> writes:
> Now how do I retrieve those array elements that do not match /a/? In Perl one
> can say @a = grep(!/a/, qw(aap noot mies)); does Ruby have a similar shortcut?

Enumerable#grep doesn't have such shortcut.  Use find_all:

  a = %w{aap noot mies}
  p a.find_all{|x| /a/ !~ x} #=> ["noot", "mies"]

-- Gotoken