sed + change small and capital letter

Question

hi all

I have the following

 echo "<x>small<X>capital" | sed s'/<x>/WORD/'g

How to change sed syntax in order to replace x and X with WORD

in this sed . sed replace only the small letter x

THX yael

Answer 1

 echo "<x>small<X>capital" | sed s'/<[Xx]>/WORD/'g

Answer 2

In GNU sed, you can use a case-insensitive modifier:

echo "<x>small<X>capital" | sed 's/<x>/WORD/ig'