Refinements bug in ruby 2.1.0dev (2013-09-08) [x86_64-linux]
I found a bug in the refinements implementation of Ruby 2.1.0. It is related to https://bugs.ruby-lang.org/issues/8722. On ruby 2.0.0p0 (2013-02-24 revision 39474) this does not occur.
The VM segfaults when the attached code is executed. The problem is that a used refinement is modified afterwards.