yet another approach

more.rx

( useful things )
: dictionary.find/xt ( string:name - xt )  find [ @d->xt ] [ drop #0 ] if ;
: getc:internal  ( -c )  &getc 2 + @ do ;
: __$ keepString 1 , , &dictionary.find/xt , ; parsing

( keymap )
9 variable: prefix:CHAR
create prefix:TABLE  256 allot

( We will lookup the keymap by name, to allow for per-application maps )

[ dup prefix:CHAR @ ==
  [ drop getc:internal
    $prefix:TABLE + @ dup 0 <> [ dip cr ] [ drop ] if 0
  ] ifTrue
  dup '| == push over tib == pop and
  [ putc
    '| $prefix:TABLE + @ do cr 0
  ] ifTrue
] is remapKeys

: (matching) ;
: bindTo: ( quote "character" - )
  getc:internal $prefix:TABLE + ! ;

[ cr
  "?        help text\n" puts
  "d<word>  documentation for word\n" puts
  "s        show stack contents\n" puts
  "p<char>  change trigger character to <char>\n" puts ] .s bindTo: ?

[ "display docs for: " puts
  getToken find
  [ cr @d->doc 0; puts ] [ drop cr "no docs found!" puts ] if
] bindTo: d

[ "display functions matching: " puts
  getToken cr (matching) ] bindTo: m

[ getc:internal dup putc !prefix:CHAR ] bindTo: p

[ getc:internal getc:internal
  drop $prefix:TABLE +
  getToken find [ @d->xt swap ! ] [ drop drop ] if
] bindTo: |

|w|words
|s|.s
|?|help