I'm new to ruby, but not to programming.  I just need a simple script that given a text file will pull out around 10% of the lines at random.  Below is what I came up with based upon a python script I wrote.  What do I need to do differently to make it more ruby-like?

    prng = Random.new
    
    File.open('english-words-partial.txt', 'w') {  |f| 
      File.readlines('english-words-full.txt').each do |line| 
        if prng.rand >= 0.9
          f.write(line) 
        end
      end
    }