>>-VAR(name)---------------------------------------------------><
1 if name is the name of a variable (that is, a symbol that has been assigned a value), or 0.
Example 7.100. Builtin function VAR
/* Following: DROP A.3; J=3 */
VAR("J") -> 1
VAR(J) -> 0 /* has tested "3" */
VAR("a.j") -> 0 /* has tested "A.3" */
VAR(2) -> 0 /* a constant symbol */
VAR("*") -> 0 /* an invalid symbol */