If i know there will be at most one newline, i start by typing "# ", then paste. If the newline gets interpreted, then the whole line is just a comment anyway.

If i know there will be at most one newline, i start by typing "# ", then paste. If the newline gets interpreted, then the whole line is just a comment anyway. It's then easy to edit the # off the start of the line before running it for real.