str1 = "replace    multiple spaces   in     this   string with a      single                    space"
str2 = "remove the decimal point and fractional parts of 3.14159 and 99.999."
str3 = "if words are 4 or more characters surrounded by spaces, replace words in this sentence with a single W"
str4 = "like str3 but now words must be between 4 and 6 characters"