global varlist;
Keyword used inside a function definition to access variables located in the global scope.
The global keyword must be the first statement in the function definition after the opening bracket. varlist is a list of one or more variables separated by commas.
See also for if else while return
Example
a=3
3
b=5
5
f(x) = {
global a, b;
return x*a + b;
}