How can I debug a single ruby ​​script in netbeans?

All of this is in a Windows XP box:

Netbeans managed to take over an existing rails project and allowed me to debug just fine, but there are several processing scripts in my project that handle non-MVC aspects. The rails project is just a queuing system for executing these scripts.

I tried to create netbeans projects using existing sources, but not for a variety of reasons.

First, since I have multiple scripts in one place, netbeans complains that I cannot add the source directory to the project because it already belongs to another project. If I put the script in my own, empty directory and try to add that directory, netbeans stalls when I try to build the project and I have to end the process from the task manager.

If I create a new project for it, delete the main main.rb file and replace it with the script I want to debug, the debug session won't start - netbeans complains that it can't find the program entry point.

It seems to me that if I can debug rails apps as easily as netbeans does, then running a single standalone script would be trivial. What am I missing?

UPDATE: Loading script and executing "Debug / Debug file" is not possible. The option is always greyed out, even for the hello world.