Listing:

    1  MODULE PNested;
    2  VAR ExitCode : INTEGER;
    3  PROCEDURE Outer;
    4  VAR o : INTEGER;
    5    PROCEDURE Inner : INTEGER;
    6    BEGIN
    7      RETURN o + 1
    8    END Inner;
    9  BEGIN
   10    o := 41;
   11    ExitCode := Inner()
   12  END Outer;
   13  BEGIN
   14    Outer
   15  END PNested.

    0 errors