Printing a string with escapes in it will render as a string normally.

  nix-repl> "meow\n\nmeowmeowmeow"
  "meow\n\nmeowmeowmeow"

But with :p on the string itself it will print it literally to the output.

  nix-repl> :p "meow\n\nmeowmeowmeow"
  meow

  meowmeowmeow

  nix-repl> builtins.listToAttrs (builtins.genList (x: { name = "meow${toString x}"; value = { meow = { inherit x; s = "meowmeow\n\n${toString x}"; }; }; }) 10)
  {
    meow0 = { ... };
    meow1 = { ... };
    meow2 = { ... };
    meow3 = { ... };
    meow4 = { ... };
    meow5 = { ... };
    meow6 = { ... };
    meow7 = { ... };
    meow8 = { ... };
    meow9 = { ... };
  }

Also, :p will expand attrs, but it will leave the strings escaped as normal if
they aren't the top level item being printed.

  nix-repl> :p builtins.listToAttrs (builtins.genList (x: { name = "meow${toString x}"; value = { meow = { inherit x; s = "meowmeow\n\n${toString x}"; }; }; }) 10)
  {
    meow0 = {
      meow = {
        s = "meowmeow\n\n0";
        x = 0;
      };
    };
    meow1 = {
      meow = {
        s = "meowmeow\n\n1";
        x = 1;
      };
    };
    meow2 = {
      meow = {
        s = "meowmeow\n\n2";
        x = 2;
      };
    };
    meow3 = {
      meow = {
        s = "meowmeow\n\n3";
        x = 3;
      };
    };
    meow4 = {
      meow = {
        s = "meowmeow\n\n4";
        x = 4;
      };
    };
    meow5 = {
      meow = {
        s = "meowmeow\n\n5";
        x = 5;
      };
    };
    meow6 = {
      meow = {
        s = "meowmeow\n\n6";
        x = 6;
      };
    };
    meow7 = {
      meow = {
        s = "meowmeow\n\n7";
        x = 7;
      };
    };
    meow8 = {
      meow = {
        s = "meowmeow\n\n8";
        x = 8;
      };
    };
    meow9 = {
      meow = {
        s = "meowmeow\n\n9";
        x = 9;
      };
    };
  }