linux shell `sed` result to variable,`line 51: 422: command not found`

Question

HTTP_CODE= `echo "[{"key":"usernameError","message":"用户名错误"}] 422" | sed -En 's/^.* ([0-9]+)$/\1/p'`
echo "${HTTP_CODE}"

echo "[{"key":"usernameError","message":"用户名错误"}] 422" | sed -En 's/^.* ([0-9]+)$/\\1/p' return 422

but `to var` command not found

Answer 1

Remove the space after the =. I made a mistake