I do agree...

Maybe it's just me, but... if I had to look at a line like this in my ruby code, it would take me an hour to understand what it does.
Yeah it surely works, it is surely optimized and my answer shouldn't be as good as this one, but sometimes, readability is just more valuable than optimization... I think. :-)

Instructions misses the "space" after the comma in the expected result if you want the result to really be "human readable", the space should be there. :)

There are some errors...
First, in the instructions, the "mode" symbol misses the ":"
Second, the example:
config.get_value( "conf", :name, :path ) == "conf"
Should definitely be included in the instructions! :)