LeftPad in Ruby

def leftPad(inputStr, paddedLength, ch='.')
  if ch.length > 1
    raise "bad input"
  end
  paddedLength = paddedLength - inputStr.length
  if paddedLength < 0
    return inputStr
  end
  
  return ch * paddedLength + inputStr   
end
puts leftPad '1', 1
puts leftPad '2', 2
puts leftPad '3', 3
puts leftPad'4', 4
puts leftPad '5', 5
puts leftPad 'hello', 7
puts leftPad "foo",  6
puts leftPad "foo", 3
puts leftPad "foobar", 3
puts leftPad "foo", 6, "?"