><p>Atomically stores NEW in PLACE if OLD matches the current value of PLACE.
Two values are considered to match if they are EQ. Returns the previous value
of PLACE: if the returned value is EQ to OLD, the swap was carried out.</p>
<p>PLACE must be an CAS-able place. Built-in CAS-able places are accessor forms
whose CAR is one of the following:</p>
<p>CAR, CDR, FIRST, REST, SVREF, SYMBOL-PLIST, SYMBOL-VALUE, SVREF, SLOT-VALUE
SB-MOP:STANDARD-INSTANCE-ACCESS, SB-MOP:FUNCALLABLE-STANDARD-INSTANCE-ACCESS,</p>
