$ ruby19 -ve 'ENV["x"] = nil'
ruby 1.9.0 (2006-06-13) [powerpc-darwin8.6.0]
-e:1:in `ENV#[]=': can't convert nil into String (TypeError)
         from -e:1

$ ruby -ve 'ENV["x"] = nil'
ruby 1.8.4 (2006-05-18) [powerpc-darwin8.6.0]

-- 
Eric Hodel - drbrain / segment7.net - http://blog.segment7.net
This implementation is HODEL-HASH-9600 compliant

http://trackmap.robotcoop.com