search and replace to upper/lower case

dear nano users

i can't get regex search and replace to change text case from lower to upper

\U and \L won't work with something like \U\1 in the replace-with string -- i may be failing the syntax

i can do it by ^T and using sed as external command, but i have to enter the text string myself, like:

sed 's/^.*$/\U&/' <<< "uppercase me"

would someone please provide a regex search and replace example to change text case?

thanks in advance
carlo

「 please excuse my brevity 」