( VALUE                     store n into pfa, return old value )

( used in the form:   )
(   n VALUE <name>    )

: value                           ( n1 --- n2 )
  -find                           ( find pfa of <name> )
  if                              ( found)
    drop                          ( drop byte count)
    dup @                         ( fetch old value)
    rot rot !                     ( store new value)
  else                            ( not found)
    1 0 ?error                    ( issue error message)
  endif
;