7.1.2 Insertion

Insertions, assignments to parts of a variable, are done using the same notation on the left-hand side of the equal sign as is used on the right-hand side to extract those very same parts (Subscripts), except that currently no more than one subscript list (between parentheses) or structure tag expression (after a period) can be specified on the left-hand side of an assignment, and summation and redirection flags are not allowed in range subscripts (Range Subscripts).

Some examples are:

x(*,i,7,/INNER) = y(3,2,*)
s.name = 'Jones'
s.3 = z