Comment 7 for bug 355883

I am mksh upstream.

This is not fixable with the current code, where keybindings are a præfix
(Esc, Esc [, ^X) plus one character plus an optional tilde.

While the input line editing code as a whole deserves overhaul, it has
fairly low priority, so this is WONTFIX for mksh.

Please use Esc+b and Esc+f instead (or bind it to other keys which
generate a “short enough” sequence), or tell your terminal emulator
to map Ctrl-Left and Ctrl-Right to Esc+b and Esc+f, respectively.