Currently when you require 'iconv' it reports a warning:
$ ruby -v -r iconv -e 0
ruby 1.9.3p125 (2012-02-16 revision 34643) [x86_64-darwin11.3.0]
[…]:in `require': iconv will be deprecated in the future, use String#encode instead.
We should remove iconv since we have String#encode now.
This issue was solved with changeset r35444.
Eric, thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.