x,←y simply appends y to x; x,←y,nl just appens y to x, then adds a newline. '' is just a string containing C code. I think you're making this more complicated

x,←y simply appends y to x; x,←y,nl just appens y to x, then adds a newline. '' is just a string containing C code. I think you're making this more complicated than it is.