rdoc/irb incompatibilities?

Hello,

I'm new to this list, sorry if this has been covered.

In Ruby 1.8.6, there seems to be incompatibilities between rdoc and
irb (I have not tried 1.9).

Both of these commands fail:
ruby -e "require 'rdoc/parsers/parse_rb'; require 'irb/ruby-token'"
ruby -e "require 'irb/ruby-token'; require 'rdoc/parsers/parse_rb'"

Both parse_rb and ruby-token define the RubyToken module with the same
constants, and requiring both results in constant redefinition
warnings, and an undefined constant error:

/usr/local/lib/ruby/1.8/irb/ruby-token.rb:253:in `def_token':
uninitialized constant RubyToken::AlreadyDefinedToken (NameError)
/usr/local/lib/ruby/1.8/rdoc/parsers/parse_rb.rb:273:in `def_token':
uninitialized constant RubyToken::AlreadyDefinedToken (NameError)

I encounter these sort of warnings and errors when I attempt to do
things like programatically invoking RubyGems to install more than one
gem (and rdoc) in a single interpreter session, or if I attempt to use
rdebug to debug code which requires rdoc.

There are comments in the RubyGems code (doc_manager and
install_command) which refer to similar problems with rdoc.

Any thoughts?  Is this a bug?  How can I work around other than not
using rdoc and irb together?

Thanks,
-- Chad