sed depends on -r to be rightmost flag to simplify the REG_EXTENDED test.

sed depends on -r to be rightmost flag to simplify the REG_EXTENDED test.

(If a flag is 1, you can multiply it by the value you want and get that value
else zero without a branch or conditional assignment.) So move -E one to the
left so FLAG_r is 1 again, and add a [+Er] suffix instead of testing
FLAG_r | FLAG_E in the users.