string.split(str) generates an Array even if string doesn't contain str. Therefore, to avoid allocating an intermediate array unnecessarily, split given string only if string contains str.
string.sub(str, ...) duplicates string even if string doesn't contain str. Therefore, opt to use string.sub!(str, ...) instead.
Summary
string.split(str)generates an Array even ifstringdoesn't containstr. Therefore, to avoid allocating an intermediate array unnecessarily,splitgivenstringonly ifstringcontainsstr.string.sub(str, ...)duplicatesstringeven ifstringdoesn't containstr. Therefore, opt to usestring.sub!(str, ...)instead.