As I understand it, Ruby 1.9 compat in IronRuby 1.0 and 1.1 was not all
complete. So, even if you force them into 1.9 mode, things may break in
unexpected ways, and you’ll probably just get frustrated. YMMV.
As Tomas said, if you want better 1.9 support, grab the latest from
http://github.com/ironruby/ironruby and build it:
If you run into an issue, the best way to get a response is going to be
create a failing test for it, and submit it as an issue, or vote up an
existing issue if it has already been reported, on the CodePlex site: