{
 "none"          => undef,
     or 
 "value"         => reference to Value Structure,
 "valueType"     => string,
     or 
 "field"         => reference to Assign Field Structure,
     or 
 "process"       => string,
     or 
 "arith"         => reference to Arith Op Assign Structure,
     or 
 "function"      => reference to Function Assign Structure,
     or 
 "dde"           => not implemented
}
Notes: All of the above keys are mutually exclusive except for the 
value and valueType keys which always appear 
together. 
Last changes to this page 4th August 1997 by jcmurphy@arsperl.org