Handle number flags

[tulir]

https://www.gnu.org/software/sed/manual/html_node/The-_0022s_0022-Command.html

number

Only replace the numberth match of the regexp.

interaction in s command Note: the POSIX standard does not specify what should happen when you mix the g and number modifiers, and currently there is no widely agreed upon meaning across sed implementations. For GNU sed, the interaction is defined to be: ignore matches before the numberth, and then match and replace all matches from the numberth on.