version: 4.3.11(5) This seems like a bug, but it seems to have been here for a few years (from the git repository, bash-3.0 displays this behaviour while bash-2.05b doesn't).
With history expansion enabled (set +H): $ echo '!!' # good !! $ echo "$(echo '!!')" # not good; !! expands echo "$(echo 'echo '!!'')" echo !! $ echo '$$' # good $$ $ echo "$(echo '$$')" # good $$
