以下のようにすると SEGV します。

% ./ruby -e '
ary = (1..100).to_a
ary.permutation(2) {|x|
  if x == [1,2]
    ObjectSpace.each_object(Array) {|o| o.clear if o == ary && o.object_id != ary.object_id }
  end
}'
-e:4: -- control frame ----------
c:0007 p:---- s:0018 b:0018 l:000017 d:000017 CFUNC  :==
c:0006 p:0006 s:0014 b:0014 l:000005 d:000013 BLOCK  -e:4
c:0005 p:---- s:0013 b:0012 l:000011 d:000011 FINISH :each
c:0004 p:---- s:0010 b:0010 l:000009 d:000009 CFUNC  :permutation
c:0003 p:0020 s:0006 b:0006 l:000005 d:000005 TOP    -e:3
c:0002 p:---- s:0003 b:0003 l:000002 d:000002 FINISH :inherited
c:0001 p:---- s:0001 b:-001 l:000000 d:000000 ------ 
---------------------------
DBG> : "-e:4:in `block in <main>'"
DBG> : "-e:3:in `permutation'"
DBG> : "-e:3:in `<main>'"
-- backtrace of native function call (Use addr2line) --
0x80f9e76
0x8117164
0x8117203
0x80c2bc5
0xb7f47420
0x805cb2b
0x8078eeb
0x81038ad
0x80fd64c
0x8103974
0x80f00b5
0x80f79a5
0x80f7522
0x80f58d5
0x80f7b7e
0x80f0d64
0x80f0e32
0x805b9f6
0x805ba38
0x8104711
0x8104698
0x810490d
0x80f00b5
0x80f79a5
0x80f7522
0x80f3ed9
0x80f7b7e
0x80f81c3
0x805aafd
0x805abac
0x8057d74
0xb7db1ea8
0x8057c91
-------------------------------------------------------
[BUG] Segmentation fault
ruby 1.9.0 (2007-10-09) [i686-linux]
-- 
[田中 哲][たなか あきら][Tanaka Akira]