Retaining the pattern characters while splitting via Regex, Ruby

I have the following string

str="HelloWorld How areYou I AmFine"

I want this string into the following array

["Hello","World How are","You I Am", "Fine"]

I have been using the following regex, it splits correctly but it also omits the matching pattern, i also want to retain that pattern. What i get is

str.split(/[a-z][A-Z]/)
 => ["Hell", "orld How ar", "ou I A", "ine"] 

It omitts the matching pattern.

Can any one help me out how to retain these characters as well in the resulting array