I was playing around with the rx function for generating regular expressions from sexps in ELISP but couldn't figure out how to generate the regular expression "\\documentclass" for use in org-export-latex-classes: (rx "\\documentclass") (rx "\\" "documentclass") (rx (char "\\") "documentclass") Which when evaluated give respectively the following outputs: "\\\\documentclass" "\\\\documentclass" "[\\]documentclass" Is "\\documentclass" equivalent to "[\\]documentclass"?---I think it is, but am not sure. Can I generate the former using rx? Edit: Whilst the question was valid I realize my motivation was not; because org-export-latex-classes use strings not regular expressions.