define Statement
A define statement is of the form
define $var := expr;
The expression expr is evaluated and the result is assigned to the
variable $var. The variable may not be defined before this statement;
it is defined by the statement and only exists until the statement sequence in
which the assignment is situated has been processed fully.
You can assign the elements of a list value to multiple variables at once:
define <$var1, $var2, ... > := expr;
The first, second, ... element of expr, which must be a list, is
assigned to the new variable $var1, $var2, ... respectively.
The number of variables must match the length of the list value.