For convience, I'll define the prompt and command here:
set prompt "date" ;# our remote command set prompt "% " ;# our shell or whatever prompt we have
Now we can do useful things:
expect $prompt ;# wait for prompt send "date\r" ;# send command expect $prompt\r\n ;# discard command echo
Finally, match and save the result and discard the next prompt:
expect -re (.*)\r\n$prompt\r\n"
Now the result is in $expect_out(1,string).
If you want to read more about this, start on page 113 of Exploring Expect.
PS: If the result might be more than 2000 characters, you'll need to use the match_max command to increase the buffer space.