Hey..  Well, I was..  There really must be something up here.

Code: (test.rb)
require 'optparse'
opts = OptionParser.new
opts.on("-s", "--size VAL", "Something to describe size") {|s| puts
"Size is: #{s}"}
opts.parse!   # the important part...

Result:
C:\temp>ruby test.rb -s "Very Big"


C:\temp>