s = .MutableBuffer~new(xrange("a", "z"))
s[5] = "E" -- "abcdEfghijklmnopqrstuvwxyz"
s[5] = "XXXX" -- "abcdXXXXijklmnopqrstuvwxyz"
s[5] = "" -- "abcdXXXXijklmnopqrstuvwxyz"
s[5, 1] = "=" -- "abcd=XXXijklmnopqrstuvwxyz"
s[5, 4] = "=" -- "abcd=ijklmnopqrstuvwxyz"
s[10, 2] = "REPLACE" -- "abcd=ijklREPLACEopqrstuvwxyz"
s[4, 99] = "" -- "abc"