* $S@ ( $: a$ -- a$ S: a.str )

Leave the string stack unchanged, and leave the string body address and
length on the data stack. "string-s-fetch"
NOTE:  In earlier versions this was call $S@S.  The trailing "S" is 

superfluous if it is understood that the only string format that
usually appears on the data stack is the Forth string format.
WARNING:  If a$ is a dynamic string, it may move at the next garbage 

collection, making a.str invalid.

dstrings ordinary primitive