I thought (naively) that writing
\tl_set:Nx \l_tmpa_tl { \tl_to_uppercase:n {text} }
would put TEXT in the variable \l_tmpa_tl (as revealed by \tl_show:N
\l_tmpa_tl). It doesn't, and nothing else that I've tried does either.
What is the recipe for getting \l_tmpa_tl to contain TEXT, starting from
text?
Andrew