It would be really stupid to open the Arethusa intercepts in a window—he’s not going to do that. But he can use this technique to conceal whatever else he’s doing in the way of decryption work. It occurs to him, however, when he gets a few lines into writing this Perl script, that if he pulls a stunt like that so early in his incarceration, the people surveilling him will know right away that he is on to them. And maybe it’s better if he lets them believe, for a while, that he suspects nothing.