Bash delete directories except that one

Ran into a scenario where I needed to delete all subdirectories of target except target/keepme/. So I want rm -rf target/subdir1 target/subdir2 ... target/subdirN with one directory omitted. I want to use grep to remove the directory I want to keep from the list so something like this should work:

1. Print the list of directories echo target/*/
2. Flip space separator to newline  tr " " "\n"
3. Remove the line for the directory to keep grep -v keepme
4. Flip newline back to space  tr "\n" " "
5. Run rm -rf on the results from steps 1-4

As a 1-liner:

rm -rf $(echo target/*/ | tr " " "\n" | grep -v keepme | tr "\n" " ")

Noting it in case I need to do it again someday ;)