Hello, I'm trying to achieve something similar to etoolbox's \patchcmd. Following some earlier discussion with Will, I decided to try the \tlp_replace_ ... functions. However, trying a minimal example: \documentclass{article} \usepackage{expl3} \CodeStart \def_new:NNn\macro 0 {TEXT} \tlp_new:N\g_temp_tlp \tlp_set:Nn\g_temp_tlp{ABCDE\macro} \tlp_replace_in:Nnn\g_temp_tlp{A}{B} \CodeStop \begin{document} \end{document} I get an error about undefined \l_tlp_replace_toks. I've not cut the burning-edge of expl3, so this may have been fixed. However, I thought I should report it. -- Joseph Wright Tel. 01604 810094 Morning Star Mobile 07974 148180 2 Dowthorpe End Earls Barton Northants NN6 0NH