Nope, ! is the escape to look something up in the terminfo database. See all the default bindings for cursor keys etc in Readline.pike. (Note that terminfo based bindings should be made after hardcoded ones, so that they can override. If for example cursor left is "^H" on some terminal, the binding order
({ "^H", backward_delete_char }), ({ "\!kl", backward_char }),
makes sure that cursor left generates backward_char on that terminal.)