
\formatted{
\def{reverse#1}{
   \push{user}    \: being paranoid.
   \set{_a}{}
   \apply{_#1{\!setx{_a}{{\!1}\!_a}}}{\1}
   \: apply creates _#1{\setx{_a}{{\1}\_a}}
   \_a
   \pop{user}
}}

\set{list}{{1}{2}{3}{\!reverse{{a}{b}{c}}}{4}{5}{6}}
before: \apply{protect#1}{{\list}}
after : \reverse{\eval{\list}}

