Why exactly the last one is parsed as a literal string and not as a line
break, I don't know. Nicolas will probably explain all. The only thing I
can say is that if there is something other than whitespace on the line
before the \\, it gets parsed as a line break; if there is only
whitespace (or nothing), it gets parsed as a string. That's probably a
rough description and not quite right in all particulars, but I hope
it's close enough.