Alt-x as Meta is not supported, DutchDaemon: Meta-. yields ® really. Use Esc+x instead (note foo-bar = hold them together, foo+bar = press them in sequence notation). ^[x means Esc+x just as ^X means Ctrl-X – Ctrl-[ is ESC in ascii(7).
Czesc vermaden, mksh feature requests (and support, I...