How to bind to the hotkey ctrl + backspace in the REPL?

General Usage
1

Following the directions in the documentation, I added the following into my startup.jl in order to make ctrl + backspace delete the previous word and ctrl + delete delete the next word:

using REPL
using REPL.LineEdit

const mykeys = Dict{Any,Any}(
  "^H"      => (s, o...) -> LineEdit.edit_delete_prev_word(s),
  "^[[3;5~" => (s, o...) -> LineEdit.edit_delete_next_word(s),
)

function customize_keys(repl)
    repl.interface = REPL.setup_interface(repl; extra_repl_keymap = mykeys)
end

atreplinit(customize_keys)

This worked, but had the unfortunate side effect that backspace without ctrl also deletes a full word. Is there a way that I can map an action to ctrl + backspace without also mapping it to backspace? I tried "^\b", but that gave me InexactError: trunc(UInt32, -56). Any ideas?