/sys$common/syshlp/helplib.hlb CXXDEMANGLE, Command Parameters  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  mangled-symbol-name

  CXXDEMANGLE accepts symbol names in their mangled form, as they might
  appear in the output from a CXXLINK/NOEXPAND command.

  If you specify a mangled symbol name using the command line interface
  and the symbol contains lowercase letters, you must place the symbol
  within quotes.  For example, $ CXXDEMANGLE "MyFunction__xic".  Quotes are
  not necessary when entering mangled symbol names using the interactive
  interface.