While reviewing the above code, I wrote a combinator to implement the pattern: swap [ quot ] dip

This allows for:
x y z --> x z [ quot ] call y --> x' y


! Copyright (C) 2013 Loryn Jenkins.
! See http://factorcode.org/license.txt for BSD license.
USING: kernel shuffle sequences ;

IN: kernel

: swip ( x y z -- x' y ) [ swapd ] dip call swap ; inline

IN: sequences

: append-back-over! ( x y z -- x-z-append! y ) [ append! ] swip ;
: append-back-over ( x y z -- x-z-append y ) [ append ] swip ;

However, subsequent editing of the program showed that this wasn't necessary. So, swip ended up the offcuts bin.