Ruby-debug-ide installation problems

Ruby
1

I’m running Kubuntu Linux 7.10 (and still very much learning Linux).

In a console I just issued the command

All did not go well:

Install required dependency ruby-debug-base? [Yn] y
Select which gem to install for your platform (i486-linux)

  1. ruby-debug-base 0.10.0 (mswin32)
  2. ruby-debug-base 0.10.0 (ruby)
  3. Skip this gem
  4. Cancel installation

2
Building native extensions. This could take a while…
ERROR: While executing gem … (Gem::Installer::ExtensionBuildError)
ERROR: Failed to build gem native extension.

ruby extconf.rb install ruby-debug-ide
sh: ruby: not found

Gem files will remain installed in
/var/lib/gems/1.8/gems/ruby-debug-base-0.10.0 for inspection.
Results logged to
/var/lib/gems/1.8/gems/ruby-debug-base-0.10.0/ext/gem_make.out

I don’t understand what this means. Can someone tell me what to do?