[sh] sed -i -E "s/old_regexp/new/g" file

sudo sed -i -E "s/^# tags:/tags:/g" /etc/datadog-agent/datadog.yaml

https://unix.stackexchange.com/questions/78625/using-sed-to-find-and-replace-complex-string-preferrably-with-regex

Using sed to find and replace complex string (preferrably with regex)