tpope/vim-rsi — pull request #10 by aaronjensen (2014-03-11 04:50:50+00:00)
Title: Add support for <M-BS> as delete-backward-word (squashed)

Although is perfectly useful already, one of the readline key
bindings I use a lot is ("delete-backward-word"). However,
implementing this is complicated by the fact that it is apparently
impossible(?) to get the actual backspace key within vim. Attempts to,
for example,

exe "set =\\"

result in being set to <80>fb, which is probably some
internal indirect reference to the termcap variable, and, moreover,
doesn't work. Inexplicably, as well, one cannot retrieve the value of
&t_xx (&t_fb specifically is what we want here) termcap options in vim
script.

As far as I know, in the modern era, terminals generally use either
or for backspace; and sometimes these are transposed with
the bindings for . My brutish solution is to bind both
and to the desired function. The consequence is that, for
some terminals, might be bound to the same as , but
I don't think means anything in readline anyhow.