$TUCK $SWAP $TYPE
$TUCK
* $TUCK ($: a$ b$ -- b$ a$ b$ )

Copy the top string stack item just below the second item. The
string value is not copied. "string-tuck" 
NOTE:  Because of essential string  space bookkeeping, the

system level implementation can be little more efficient than

the high-level definition:

: $TUCK  $SWAP $OVER ;


 
 dstrings   ordinary primitive