Would anyone happen to know what I would change in the scrypt below so that it would check for between 1 and up to 3 missing characters?

The reason I'm thinking this may be the problem is, I'm using a wireless keyboard and sometimes when typing if your sat in the wrong place the keystrokes aren't always picked up.

 # delete one char
  passphrase.length.times do |i|
    testphrase = passphrase.dup
    testphrase = testphrase[0,i] + testphrase[(i+1)..-1]
    list << testphrase
  end 

Thanks