irb (and a little Ruby knowledge) is great for system tasks, especially on 
Windows where the command-line tools are generally lacking.

For example: 
We're migrating from VC++ 6.0 to VC++ 7.0 (Visual Studio .NET, or whatever 
the heck they call it now) so we had to migrate a bunch of projects to to 
the new project format.  Now instead of .dsw and .dsp files they use 
..vcproj and .sln files.  These things are all over the directory tree so 
chasing them all down and adding them to cvs is a bit of a pain (and there 
are about 20 of them)...  But it's no problem in irb:

> projfiles = Dir["**/*.vcproj"]
  [ list of vcproj files ]
> slnfiles = Dir["**/*.sln"]
  [ list of sln files ]
> files = projfiles + slnfiles
  [ list of both ]
> files.each {|f|
>   `cvs add #{f}`
> }

....done. 

Phil