cannot paste lines into Gnuplot

[fpeos]

Since I upgraded to MacOS Big Sur, I am no longer able to paste a few command lines from a terminal or Aquamacs into Gnuplot. It does not recognize the newline character and falsely tries to interpret all lines as a single commands:

set xlabel "x" set ylabel "y" plot "tmp.txt" u 4:6 w p

When it paste these lines into Gunplot's prompt, they also show up white on black.

I updated to macOS 11.2.2., manually reinstalled Ports and Gnuplot, and followed the directions under ticket #62364 but it still does not work. Since I cut and paste a few lines often, a fix would be appreciated. Thanks for your time.