This is TeX, Version 2.2 (INITEX) 13 JUN 1987 21:45 **\catcode`↑7 \x ! TeX capacity exceeded, sorry [text input levels=6]. <insert> \x↑↑? ↑↑? <insert> \x ↑↑?↑↑? <insert> \x ↑↑?↑↑? <insert> \x ↑↑?↑↑? <insert> \x ↑↑?↑↑? <insert> \x ↑↑?↑↑? <*> \catcode`↑7 \x If you really absolutely need more capacity, you can ask a wizard to enlarge me. debug # (-1 to exit): No pages of output.