ruby-debug for Ruby 1.9.x provides the exact same functionality you have with the Ruby 1.8 ruby-debug, and more. A “jump” command was added on 9/3/09; it allows you to change the next line to be executed, and even allows you to jump through stack frames, to a different frame of execution. This is available in NetBeans as well as the command-line rdebug.
The command-line version is provided with the ruby-debug19 gem. The IDE version has been incorporated into the same ruby-debug-ide gem, with preview features distributed with the ruby-debug-ide19 gem.