Hi,

In [ruby-talk :15857 ] the message: "[ruby-talk:15857] irb/completion
BUG? ", on May/28 19:10(JST) "Hee-Sob Park" writes:

>When  I try irb -r irb/completion and type "ab.<TAB>",
>
>following error message occurred and resulted in confused terminal state.
>
>irb(main):002:0> ab./usr/local/lib/ruby/1.6/irb/completion.rb:31:in `eval':
>(eval):1:in `irb_binding': undefined local variable or method `ab'
>for

Perhaps, You use an old version of irb/completion. Down load from RAA. 

  http://www.ruby-lang.org/en/raa-list.rhtml?name=irb-tools

or

Use irb bundled with latest Ruby-1.6(stable-snapshot.tar.gz) or
Ruby-1.7 (try snapshot.tar.gz).

-- keiju