Using rio I noticed that
1. require 'rio', although successful, returns false
2. rio(...) < '...' generates warnings, if in verbose mode:

irb(main):001:0> require 'rubygems'
=> true
irb(main):002:0> require 'rio'
=> false
irb(main):003:0> $VERBOSE = true
=> true
irb(main):004:0> rio('test') < "Hello\n"
/usr/local/lib/ruby/gems/1.8/gems/rio-0.3.2/lib/rio/cp.rb:181: warning: useless use of < in void context
/usr/local/lib/ruby/gems/1.8/gems/rio-0.3.2/lib/rio/cp.rb:273:      warning: useless use of > in void context
=> #<Rio:0x20172a32:"path:test" (Stream::Reset)>
irb(main):005:0>