With the defglobal construct, global variables can be defined, set, and
accessed within the CLIPS environment. Global variables can be accessed
as part of the pattern matching process, but changing them does not invoke
the pattern matching process. The bind function is used to set the value
of global variables.
The syntax of the defglobal construct is:
<defglobal-construct> ::= (defglobal [<defmodule-name>]
<global-assignment>*)
<global-assignment> ::= <global-variable> = <expression>
<global-variable> ::= ?*<symbol>*