fails:String#each splits self using the supplied record separator and passes each substring to the block
fails:String#each taints substrings that are passed to the block if self is tainted
fails:String#each passes self as a whole to the block if the separator is nil
fails:String#each appends multiple successive newlines together when the separator is an empty string
fails:String#each uses $/ as the separator when none is given
fails:String#each yields subclass instances for subclasses
fails:String#each returns self
fails:String#each tries to convert the separator to a string using to_str
fails:String#each raises a RuntimeError if the string is modified while substituting
fails:String#each raises a TypeError when the separator can't be converted to a string
